Make code C conformant.

Originally committed as revision 12217 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/mem.h

@@ -36,7 +36,7 @@
     #define DECLARE_ALIGNED(n,t,v)      __declspec(align(n)) t v
     #define DECLARE_ASM_CONST(n,t,v)    __declspec(align(n)) static const t v
 #else
-    #warning No align and asm directives, this might fail.
+//  #warning No align and asm directives, this might fail.
     #define DECLARE_ALIGNED(n,t,v)      t v
     #define DECLARE_ASM_CONST(n,t,v)    static const t v
 #endif