move SK_MMAP_SUPPORT into SkPreConfig, so we can know about its availability

trunk/src/ports/SkFontHost_freetype_mac.cpp

Index: trunk/src/ports/SkFontHost_freetype_mac.cpp
===================================================================
--- trunk/src/ports/SkFontHost_freetype_mac.cpp	(revision 8197)
+++ trunk/src/ports/SkFontHost_freetype_mac.cpp	(working copy)
@@ -6,7 +6,6 @@
  */
 
 #include "SkFontHost.h"
-#include "SkMMapStream.h"
 #include "SkTypefaceCache.h"
 
 #define FONT_PATH   "/Library/Fonts/Skia.ttf"
@@ -26,7 +25,11 @@
 };
 
 static FTMacTypeface* create_from_path(const char path[]) {
-    SkStream* stream = new SkMMAPStream(path);
+    SkStream* stream = SkStream::NewFromFile(path);
+    if (!stream) {
+        return NULL;
+    }
+
     size_t size = stream->getLength();
     SkASSERT(size);
     FTMacTypeface* tf = new FTMacTypeface(SkTypeface::kNormal,