Fixed some warnings on GCC

Mozilla has recently made using NULL as integer an error (via
-Werror=conversion-null GCC flag), which caused ANGLE to no longer compile on
mingw in Mozilla tree. The ones that may not be obvious are removal of some <0
checks. They are not needed because they were done on unsigned types.

Author: Jacek Caban
http://codereview.appspot.com/6679049

(With changes to apply to dx11proto branch)

git-svn-id: https://angleproject.googlecode.com/svn/branches/dx11proto@1464 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/libGLESv2/renderer/Renderer11.cpp b/src/libGLESv2/renderer/Renderer11.cpp
index 15c9338..9ff3e34 100644
--- a/src/libGLESv2/renderer/Renderer11.cpp
+++ b/src/libGLESv2/renderer/Renderer11.cpp
@@ -178,14 +178,14 @@
 
 int Renderer11::generateConfigs(ConfigDesc **configDescList)
 {
-    int numRenderFormats = sizeof(RenderTargetFormats) / sizeof(RenderTargetFormats[0]);
-    int numDepthFormats = sizeof(DepthStencilFormats) / sizeof(DepthStencilFormats[0]);
+    unsigned int numRenderFormats = sizeof(RenderTargetFormats) / sizeof(RenderTargetFormats[0]);
+    unsigned int numDepthFormats = sizeof(DepthStencilFormats) / sizeof(DepthStencilFormats[0]);
     (*configDescList) = new ConfigDesc[numRenderFormats * numDepthFormats];
     int numConfigs = 0;
     
-    for (int formatIndex = 0; formatIndex < numRenderFormats; formatIndex++)
+    for (unsigned int formatIndex = 0; formatIndex < numRenderFormats; formatIndex++)
     {
-        for (int depthStencilIndex = 0; depthStencilIndex < numDepthFormats; depthStencilIndex++)
+        for (unsigned int depthStencilIndex = 0; depthStencilIndex < numDepthFormats; depthStencilIndex++)
         {
             DXGI_FORMAT renderTargetFormat = RenderTargetFormats[formatIndex];