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/Image.cpp b/src/libGLESv2/renderer/Image.cpp
index b069d1c..e62c3fb 100644
--- a/src/libGLESv2/renderer/Image.cpp
+++ b/src/libGLESv2/renderer/Image.cpp
@@ -317,7 +317,7 @@
 
         IDirect3DDevice9 *device = mRenderer->getDevice(); // D3D9_REPLACE
 
-        HRESULT result = device->CreateTexture(requestWidth, requestHeight, levelToFetch + 1, NULL, d3dFormat,
+        HRESULT result = device->CreateTexture(requestWidth, requestHeight, levelToFetch + 1, 0, d3dFormat,
                                                     poolToUse, &newTexture, NULL);
 
         if (FAILED(result))