Increase MSVC warning level to 4.

There are some exceptions, a subset of the exceptions used by Chromium. They didn't seem to be useful warnings.

In code which we don't change much, like the preprocessor, I just suppressed the warnings in the specific files rather than changing the code.

There should be no functional changes in this patch.
Review URL: https://codereview.appspot.com/5570066

git-svn-id: https://angleproject.googlecode.com/svn/trunk@964 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/libGLESv2/Program.cpp b/src/libGLESv2/Program.cpp
index bcab6f7..561852e 100644
--- a/src/libGLESv2/Program.cpp
+++ b/src/libGLESv2/Program.cpp
@@ -270,7 +270,7 @@
 
 GLint Program::getUniformLocation(std::string name)
 {
-    int subscript = 0;
+    unsigned int subscript = 0;
 
     // Strip any trailing array operator and retrieve the subscript
     size_t open = name.find_last_of('[');