Fix gcc warnings

[rouault]

This fixes warnings that would otherwise be emitted by ``gcc -Wall test.c -c -Iinclude -mavx2 -O2 -mfma -ffp-contract=off" on the below test.c

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <x86intrin.h>

#include <sleefinline_sse4.h>
#include <sleefinline_sse2.h>
#include <sleefinline_avx.h>
#include <sleefinline_avx2.h>
#include <sleefinline_avx2128.h>

Warnings emitted before this pull request:

In file included from test.c:6:
include/sleefinline_sse4.h:23: warning: ignoring #pragma STDC FP_CONTRACT [-Wunknown-pragmas]
   23 | #pragma STDC FP_CONTRACT OFF
      | 
In file included from test.c:7:
include/sleefinline_sse2.h:23: warning: ignoring #pragma STDC FP_CONTRACT [-Wunknown-pragmas]
   23 | #pragma STDC FP_CONTRACT OFF
      | 
In file included from test.c:8:
include/sleefinline_avx.h:23: warning: ignoring #pragma STDC FP_CONTRACT [-Wunknown-pragmas]
   23 | #pragma STDC FP_CONTRACT OFF
      | 
In file included from test.c:9:
include/sleefinline_avx2.h:23: warning: ignoring #pragma STDC FP_CONTRACT [-Wunknown-pragmas]
   23 | #pragma STDC FP_CONTRACT OFF
      | 
In file included from test.c:10:
include/sleefinline_avx2128.h:23: warning: ignoring #pragma STDC FP_CONTRACT [-Wunknown-pragmas]
   23 | #pragma STDC FP_CONTRACT OFF
      | 
In file included from test.c:10:
include/sleefinline_avx2128.h:1452:13: warning: ‘vstoreu_v_p_vq’ defined but not used [-Wunused-function]
 1452 | static void vstoreu_v_p_vq(void *p, vquad_avx2128_sleef vq) {
      |             ^~~~~~~~~~~~~~
include/sleefinline_avx2128.h:1432:28: warning: ‘loadu_vq_p_avx2128_sleef’ defined but not used [-Wunused-function]
 1432 | static vquad_avx2128_sleef loadu_vq_p_avx2128_sleef(void *p) {
      |                            ^~~~~~~~~~~~~~~~~~~~~~~~
include/sleefinline_avx2128.h:1170:13: warning: ‘vstoreu_v_p_vi_avx2128_sleef’ defined but not used [-Wunused-function]
 1170 | static void vstoreu_v_p_vi_avx2128_sleef(int32_t *p, vint_avx2128_sleef v) { _mm_storeu_si128((__m128i *)p, v); }
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/sleefinline_avx2128.h:1169:27: warning: ‘vloadu_vi_p_avx2128_sleef’ defined but not used [-Wunused-function]
 1169 | static vint_avx2128_sleef vloadu_vi_p_avx2128_sleef(int32_t *p) { return _mm_loadu_si128((__m128i *)p); }
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~
In file included from test.c:9:
include/sleefinline_avx2.h:1457:25: warning: ‘loadu_vq_p_avx2_sleef’ defined but not used [-Wunused-function]
 1457 | static vquad_avx2_sleef loadu_vq_p_avx2_sleef(void *p) {
      |                         ^~~~~~~~~~~~~~~~~~~~~
include/sleefinline_avx2.h:1175:13: warning: ‘vstoreu_v_p_vi_avx2_sleef’ defined but not used [-Wunused-function]
 1175 | static void vstoreu_v_p_vi_avx2_sleef(int32_t *p, vint_avx2_sleef v) { _mm_storeu_si128((__m128i *)p, v); }
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~
include/sleefinline_avx2.h:1174:24: warning: ‘vloadu_vi_p_avx2_sleef’ defined but not used [-Wunused-function]
 1174 | static vint_avx2_sleef vloadu_vi_p_avx2_sleef(int32_t *p) { return _mm_loadu_si128((__m128i *)p); }
      |                        ^~~~~~~~~~~~~~~~~~~~~~
include/sleefinline_avx2.h:1173:13: warning: ‘vstoreu_v_p_vi2_avx2_sleef’ defined but not used [-Wunused-function]
 1173 | static void vstoreu_v_p_vi2_avx2_sleef(int32_t *p, vint2_avx2_sleef v) { _mm256_storeu_si256((__m256i *)p, v); }
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~
include/sleefinline_avx2.h:1172:25: warning: ‘vloadu_vi2_p_avx2_sleef’ defined but not used [-Wunused-function]
 1172 | static vint2_avx2_sleef vloadu_vi2_p_avx2_sleef(int32_t *p) { return _mm256_loadu_si256((__m256i const *)p); }
      |                         ^~~~~~~~~~~~~~~~~~~~~~~
In file included from test.c:8:
include/sleefinline_avx.h:1546:24: warning: ‘loadu_vq_p_avx_sleef’ defined but not used [-Wunused-function]
 1546 | static vquad_avx_sleef loadu_vq_p_avx_sleef(void *p) {
      |                        ^~~~~~~~~~~~~~~~~~~~
include/sleefinline_avx.h:1184:23: warning: ‘vloadu_vi_p_avx_sleef’ defined but not used [-Wunused-function]
 1184 | static vint_avx_sleef vloadu_vi_p_avx_sleef(int32_t *p) { return _mm_loadu_si128((__m128i *)p); }
      |                       ^~~~~~~~~~~~~~~~~~~~~
include/sleefinline_avx.h:1172:24: warning: ‘vloadu_vi2_p_avx_sleef’ defined but not used [-Wunused-function]
 1172 | static vint2_avx_sleef vloadu_vi2_p_avx_sleef(int32_t *p) {
      |                        ^~~~~~~~~~~~~~~~~~~~~~
In file included from test.c:7:
include/sleefinline_sse2.h:1447:25: warning: ‘loadu_vq_p_sse2_sleef’ defined but not used [-Wunused-function]
 1447 | static vquad_sse2_sleef loadu_vq_p_sse2_sleef(void *p) {
      |                         ^~~~~~~~~~~~~~~~~~~~~
include/sleefinline_sse2.h:1166:24: warning: ‘vloadu_vi_p_sse2_sleef’ defined but not used [-Wunused-function]
 1166 | static vint_sse2_sleef vloadu_vi_p_sse2_sleef(int32_t *p) { return _mm_loadu_si128((__m128i *)p); }
      |                        ^~~~~~~~~~~~~~~~~~~~~~
include/sleefinline_sse2.h:1163:25: warning: ‘vloadu_vi2_p_sse2_sleef’ defined but not used [-Wunused-function]
 1163 | static vint2_sse2_sleef vloadu_vi2_p_sse2_sleef(int32_t *p) { return _mm_loadu_si128((__m128i *)p); }
      |                         ^~~~~~~~~~~~~~~~~~~~~~~
In file included from test.c:6:
include/sleefinline_sse4.h:1437:25: warning: ‘loadu_vq_p_sse4_sleef’ defined but not used [-Wunused-function]
 1437 | static vquad_sse4_sleef loadu_vq_p_sse4_sleef(void *p) {
      |                         ^~~~~~~~~~~~~~~~~~~~~
include/sleefinline_sse4.h:1166:24: warning: ‘vloadu_vi_p_sse4_sleef’ defined but not used [-Wunused-function]
 1166 | static vint_sse4_sleef vloadu_vi_p_sse4_sleef(int32_t *p) { return _mm_loadu_si128((__m128i *)p); }
      |                        ^~~~~~~~~~~~~~~~~~~~~~
include/sleefinline_sse4.h:1163:25: warning: ‘vloadu_vi2_p_sse4_sleef’ defined but not used [-Wunused-function]
 1163 | static vint2_sse4_sleef vloadu_vi2_p_sse4_sleef(int32_t *p) { return _mm_loadu_si128((__m128i *)p); }
      |                         ^~~~~~~~~~~~~~~~~~~~~~~