use sse2 intrinsics for lrint/lrintf only on windows x64

[sezero]

Fixes https://github.com/libsndfile/libsamplerate/issues/187 Fixes https://github.com/libsndfile/libsamplerate/pull/188 Fixes https://github.com/libsndfile/libsamplerate/issues/191

CC: @rfomin

[rfomin]

LGTM

[evpobr]

Do we really need to limit SSE2 to x64?

https://github.com/libsndfile/libsndfile/blob/71f7bde180ade1869542d36483bc2e2c809c2189/cmake/CheckCPUArch.cmake#L17-L23

[sezero]

Do we really need to limit SSE2 to x64?

No, we don't. But can you guarantee that __SSE2__ is defined on x86?

[sezero]

Do we really need to limit SSE2 to x64?

No, we don't. But can you guarantee that __SSE2__ is defined on x86?

E.g.: see the build error I noted in #191

[sezero]

Any verdict ?

[evpobr]

Not always: https://stackoverflow.com/questions/18563978/detect-the-availability-of-sse-sse2-instruction-set-in-visual-studio

[evpobr]

Any verdict ?

Not sure redefining lrintf is good idea.

[sezero]

Not sure redefining lrintf is good idea.

I don't see the harm since we're doing it privately - but if you want static inlines, tell me.

[sezero]

Anyways, I force-pushed a version that keeps the inlines as inlines - no redefines.

[evpobr]

Thanks @sezero !