Add FLAC__SSE_SUPPORTED and FLAC__SSE2_SUPPORTED flags.

* Allow compiling using GCC GCC w/o SSE support.
* Allow SSE4.1 intrinsic functions to be enabled.

Patch-from: lvqcl <lvqcl.mail@gmail.com>
Add __INTEL_COMPILER to _MSC_VER #ifdefs.

Patch-from: lvqcl <lvqcl.mail@gmail.com>
Remove redundant inline macro def.

The inline macro already exists in include/share/compat.h.

Patch-from: lvqcl <lvqcl.mail@gmail.com>
lpc_intrin_sse2.c : Add RESIDUAL16_RESULT macro.

RESIDUAL16_RESULT is analogous to the existing RESIDUAL_RESULT macro
and simplifies the code a little.

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