Fix build on windows and mac

Replaced all occurrences of #if* __WXMSW__ with WIN32,
and all occurrences of __WXMAC_OSX__ with MAC_OSX, and made
sure those are defined appropriately in the makefile and bitcoin-qt.pro.

src/main.h

@@ -927,7 +927,7 @@ public:
         fflush(fileout);
         if (!IsInitialBlockDownload() || (nBestHeight+1) % 500 == 0)
         {
-#ifdef __WXMSW__
+#ifdef WIN32
             _commit(_fileno(fileout));
 #else
             fsync(fileno(fileout));