Fix a bunch of implicit casts detected by the Win64 compiler

samples/shell.cc

Index: samples/shell.cc
diff --git a/samples/shell.cc b/samples/shell.cc
index db0cc1a930aa22a21b82a887fb362b1b8bc65944..821ef75a7666991a05af9b8cdc1c8df51d5b480d 100644
--- a/samples/shell.cc
+++ b/samples/shell.cc
@@ -205,7 +205,7 @@ v8::Handle<v8::String> ReadFile(const char* name) {
   char* chars = new char[size + 1];
   chars[size] = '\0';
   for (int i = 0; i < size;) {
-    int read = fread(&chars[i], 1, size - i, file);
+    int read = static_cast<int>(fread(&chars[i], 1, size - i, file));
     i += read;
   }
   fclose(file);