Rename IslTextureTarget to IsInternalTextureTarget.

TEXTURE_EXTERNAL is not considered an internal texture target.
Review URL: https://codereview.appspot.com/5556067

git-svn-id: https://angleproject.googlecode.com/svn/trunk@955 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/libGLESv2/libGLESv2.cpp b/src/libGLESv2/libGLESv2.cpp
index bd000ec..e71ec28 100644
--- a/src/libGLESv2/libGLESv2.cpp
+++ b/src/libGLESv2/libGLESv2.cpp
@@ -1022,7 +1022,7 @@
 
     try
     {
-        if (!gl::IsTextureTarget(target))
+        if (!gl::IsInternalTextureTarget(target))
         {
             return error(GL_INVALID_ENUM);
         }
@@ -1311,7 +1311,7 @@
 
     try
     {
-        if (!gl::IsTextureTarget(target))
+        if (!gl::IsInternalTextureTarget(target))
         {
             return error(GL_INVALID_ENUM);
         }
@@ -2976,7 +2976,7 @@
             {
                 attachmentObjectType = attachmentType;
             }
-            else if (gl::IsTextureTarget(attachmentType))
+            else if (gl::IsInternalTextureTarget(attachmentType))
             {
                 attachmentObjectType = GL_TEXTURE;
             }
@@ -5392,7 +5392,7 @@
 
     try
     {
-        if (!gl::IsTextureTarget(target))
+        if (!gl::IsInternalTextureTarget(target))
         {
             return error(GL_INVALID_ENUM);
         }