Add ssse3 implementation of __memcmp16.

__memcmp16 was missing in x86. Also added C-version for backward
compatibility. Added bionic test for __memcmp16 and for wmemcmp.

Change-Id: I33718441e7ee343cdb021d91dbeaf9ce2d4d7eb4
Signed-off-by: Alexander Ivchenko <alexander.ivchenko@intel.com>
diff --git a/libc/arch-x86/x86.mk b/libc/arch-x86/x86.mk
index 3924ce3..19c1402 100644
--- a/libc/arch-x86/x86.mk
+++ b/libc/arch-x86/x86.mk
@@ -27,6 +27,7 @@
 	arch-x86/string/ssse3-strcpy-atom.S \
 	arch-x86/string/ssse3-memcmp-atom.S \
 	arch-x86/string/ssse3-wmemcmp-atom.S \
+	arch-x86/string/ssse3-memcmp16-atom.S \
 	arch-x86/string/ssse3-wcscat-atom.S \
 	arch-x86/string/ssse3-wcscpy-atom.S
 else
@@ -38,6 +39,7 @@
 	arch-x86/string/strncmp.S \
 	arch-x86/string/strcat.S \
 	arch-x86/string/memcmp.S \
+	string/memcmp16.c \
 	string/strcpy.c \
 	string/strncat.c \
 	string/strncpy.c \