Added a check against OSX 10.6 to enable better selection of when to provide custom cosf etc. definition.

This change has been introduced to address recurcsion problems in 10.7 in the ac3d plugin.

include/osg/Math

@@ -37,6 +37,11 @@
     #if (__GNUC__ < 4)
         #define APPLE_PRE_10_2
     #endif
+
+    #if (MAC_OS_X_VERSION_MIN_REQUIRED <  MAC_OS_X_VERSION_10_6)
+        #define APPLE_PRE_10_6
+    #endif
+    
 #endif
 #endif
 
@@ -45,7 +50,7 @@
 #endif
 
 #if defined (sun) || \
-    defined (__APPLE__) || \
+    defined (APPLE_PRE_10_6) || \
     (defined (_AIX) && defined (__GNUC__))
 
     #include <float.h>