Get rid of TARGET_CARBON as well

Don't define this symbol in configure and don't test for it.

Also remove a stray reference to wxUSE_OSX_CARBON not removed by the previous
commit.

include/wx/platform.h

@@ -289,10 +289,6 @@
         /*  __DARWIN__ is our own define to mean OS X or pure Darwin */
 #        ifndef __DARWIN__
 #            define __DARWIN__ 1
-#        endif
-        /*  NOTE: TARGET_CARBON is actually a 0/1 and must be 1 for OS X */
-#        ifndef TARGET_CARBON
-#            define TARGET_CARBON 1
 #        endif
         /* OS X uses unsigned long size_t for both ILP32 and LP64 modes. */
 #        if !defined(wxSIZE_T_IS_UINT) && !defined(wxSIZE_T_IS_ULONG)