Fixed 3DNow! detection for clang llvm

configure

@@ -17219,17 +17219,20 @@ int
 main ()
 {
 
+        void *p = 0;
+        _m_prefetch(p);
 
   ;
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
+if ac_fn_c_try_link "$LINENO"; then :
 
         have_gcc_3dnow=yes
 
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
         { $as_echo "$as_me:${as_lineno-$LINENO}: result: $have_gcc_3dnow" >&5
 $as_echo "$have_gcc_3dnow" >&6; }
         CFLAGS="$save_CFLAGS"

configure.in

@@ -459,12 +459,14 @@ AC_HELP_STRING([--enable-3dnow], [use MMX assembly routines [[default=yes]]]),
         amd3dnow_CFLAGS="-m3dnow"
         CFLAGS="$save_CFLAGS $amd3dnow_CFLAGS"
 
-        AC_TRY_COMPILE([
+        AC_TRY_LINK([
         #include <mm3dnow.h>
         #ifndef __3dNOW__
         #error Assembler CPP flag not enabled
         #endif
         ],[
+        void *p = 0;
+        _m_prefetch(p);
         ],[
         have_gcc_3dnow=yes
         ])