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>
diff --git a/src/libFLAC/stream_encoder_intrin_sse2.c b/src/libFLAC/stream_encoder_intrin_sse2.c
index ac2e69f..9852175 100644
--- a/src/libFLAC/stream_encoder_intrin_sse2.c
+++ b/src/libFLAC/stream_encoder_intrin_sse2.c
@@ -36,12 +36,14 @@
 
 #ifndef FLAC__NO_ASM
 #if (defined FLAC__CPU_IA32 || defined FLAC__CPU_X86_64) && defined FLAC__HAS_X86INTRIN
+#include "private/stream_encoder.h"
+#ifdef FLAC__SSE2_SUPPORTED
 
 #include <stdlib.h>    /* for abs() */
 #include <emmintrin.h> /* SSE2 */
 #include "FLAC/assert.h"
-#include "private/stream_encoder.h"
 
+FLAC__SSE_TARGET("sse2")
 void FLAC__precompute_partition_info_sums_intrin_sse2(const FLAC__int32 residual[], FLAC__uint64 abs_residual_partition_sums[],
 		unsigned residual_samples, unsigned predictor_order, unsigned min_partition_order, unsigned max_partition_order, unsigned bps)
 {
@@ -157,5 +159,6 @@
 	}
 }
 
+#endif /* FLAC__SSE2_SUPPORTED */
 #endif /* (FLAC__CPU_IA32 || FLAC__CPU_X86_64) && FLAC__HAS_X86INTRIN */
 #endif /* FLAC__NO_ASM */