configure.ac: fix linking the OSX UI module if the AVFoundation framework...

configure.ac: fix linking the OSX UI module if the AVFoundation framework isn't present (read: OSX 10.6)

configure.ac

@@ -3760,7 +3760,10 @@ then
   VLC_ADD_OBJCFLAGS([macosx], [-fobjc-exceptions] )
   VLC_ADD_PLUGIN([macosx])
 
-  VLC_ADD_LIBS([macosx], [-Wl,-framework,QTKit -Wl,-framework,AVFoundation -Wl,-framework,IOKit -Wl,-framework,AddressBook -Wl,-framework,WebKit -Wl,-framework,CoreAudio -Wl,-framework,SystemConfiguration -Wl,-framework,ScriptingBridge])
+  VLC_ADD_LIBS([macosx], [-Wl,-framework,QTKit -Wl,-framework,IOKit -Wl,-framework,AddressBook -Wl,-framework,WebKit -Wl,-framework,CoreAudio -Wl,-framework,SystemConfiguration -Wl,-framework,ScriptingBridge])
+
+  AC_CHECK_HEADERS(AVFoundation/AVFoundation.h,
+                       [VLC_ADD_LIBS([macosx],[-Wl,-framework,AVFoundation])])
 
   if test ! -d ${CONTRIB_DIR}/Sparkle.framework
   then