Check function prototype in check_asm function to avoid compiler warnings.

patch by Marc Mason, mpeg.blue free fr


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@16188 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

configure

@@ -512,7 +512,7 @@ check_asm(){
     asm="$2"
     shift 2
     check_cc "$@" <<EOF && enable $name || disable $name
-int foo(void){ __asm__ volatile($asm); }
+void foo(void){ __asm__ volatile($asm); }
 EOF
 }