cpu.h : Only define FLAC__SSE_SUPPORTED if FLAC__HAS_X86INTRIN is set.

Patch-from: lvqcl <lvqcl.mail@gmail.com>
fixed_intrin_sse[23].c : Simplify  XMM -> int64 conversion.

Patch-from: lvqcl <lvqcl.mail@gmail.com>