Fixes to FramebufferAttachment enum group

GL_MAX_COLOR_ATTACHMENTS is not framebuffer attachment.

GL_STENCIL_ATTACHMENT (and EXT and OES variants) are framebuffer
attachments.
diff --git a/xml/gl.xml b/xml/gl.xml
index 28f58f8..cfdbbe7 100644
--- a/xml/gl.xml
+++ b/xml/gl.xml
@@ -3316,9 +3316,6 @@
         </group>
 
         <group name="FramebufferAttachment">
-            <enum name="GL_MAX_COLOR_ATTACHMENTS"/>
-            <enum name="GL_MAX_COLOR_ATTACHMENTS_EXT"/>
-            <enum name="GL_MAX_COLOR_ATTACHMENTS_NV"/>
             <enum name="GL_COLOR_ATTACHMENT0"/>
             <enum name="GL_COLOR_ATTACHMENT0_EXT"/>
             <enum name="GL_COLOR_ATTACHMENT0_NV"/>
@@ -3388,6 +3385,9 @@
             <enum name="GL_DEPTH_STENCIL_ATTACHMENT"/>
             <enum name="GL_DEPTH_ATTACHMENT_EXT"/>
             <enum name="GL_DEPTH_ATTACHMENT_OES"/>
+            <enum name="GL_STENCIL_ATTACHMENT"/>
+            <enum name="GL_STENCIL_ATTACHMENT_EXT"/>
+            <enum name="GL_STENCIL_ATTACHMENT_OES"/>
         </group>
 
         <group name="RenderbufferTarget">