Fixed broken build of mksnapshot on Windows as there was warnings against

the use of fopen. Change use of fopen to OS::FOpen to get rid of warning.
Review URL: http://codereview.chromium.org/2846

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@303 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mksnapshot.cc

@@ -116,7 +116,7 @@ static int* counter_callback(const wchar_t* name) {
 static int WriteInternalSnapshotToFile(const char* filename,
                                        const char* str,
                                        int size) {
-  FILE* f = fopen(filename, "wb");
+  FILE* f = i::OS::FOpen(filename, "wb");
   if (f == NULL) {
     i::OS::PrintError("Cannot open file %s for reading.\n", filename);
     return 0;