General cleanup for Wall warnings and typos.

[munroesj52]

* src/pveclib/vec_common_ppc.h (__VEC_U_128):
Correct typedef for member i128.
* src/pveclib/vec_f32_ppc.h (vec_xvxexpsp):
Remove unused const var zero.
* src/pveclib/vec_f64_ppc.h (vec_xviexpdp):
Remove unused var t128.
* src/testsuite/arith128_test_f32.c (test_extract_insert_f32):
Remove unused var sigs.
* src/testsuite/arith128_test_f64.c (test_extract_insert_f64):
Remove unused var sigs.
* src/testsuite/vec_f64_dummy.c:
Move #endif matching #ifdef _ARCH_PWR8 up.  

Guard the vector double tests while leaving the gather/scatter matrix transpose test enabled for all targets.

* src/testsuite/vec_int128_dummy.c
(example_print_vint128 [__GNUC__ > 9]): long long format
warn corrected after GCC 9.

Signed-off-by: Steven Munroe munroesj52@gmail.com