Large bundle of OS X tweaks by Eric P. (basis of the 10.9-compatible

pre-release made in Dec. 2013):
 * Fix OS X 10.9 issue of current directory set by Finder
   to something else than folder where app bundle resides.
 * Some Mac OS X build / project changes & updates.
 * Adjustments to Mac OS X fontconfig config file, to avoid warnings
   and make things more robust.
 * Updates to some #include's to catch up with newer library revisions.
 * Tweaks to pixel read/write on Apple.
 * Introduction of 'intprt_t' casting to avoid warnings on x64.
 * Some additional debugging output.
 * Logging stderr & stdout to /tmp/tuxpaint.log
Untested (I don't have a Mac!)

src/im.c

@@ -484,7 +484,7 @@ static int charmap_add(CHARMAP* cm, int section, char* seq, const wchar_t* unico
 
   /* For now, we only utilize one-character flags */
   if(strlen(flag) > 1) {
-    fprintf(stderr, "%04X: Multi-character flag, truncated.\n", (int)unicode);
+    fprintf(stderr, "%04X: Multi-character flag, truncated.\n", (int)(intptr_t)unicode);        //EP added (intptr_t) to avoid warning on x64
   }
 
   return sm_add(&cm->sections[section], seq, unicode, flag[0]);