Remove on static initializer in GrGpu.cpp

Remove on static initializer in GrGpu.cpp

This is another go for the patch that was initially
submitted at http://codereview.appspot.com/5504073/ but
crashed the 'gm' unit test.

A problem with the previous implementation is that the
GrStencilSettings ::isDisabled() and ::doesWrite() methods can
modify the object's fFlags member if it is 0, and this will
crash at runtime when doing this for a static constant
object/structure.

I'm not sure why this wasn't triggered previously.

We solve the issue by modifying the implementation of
GR_STATIC_CONST_STENCIL and GR_STATIC_CONST_STENCIL macros to
compute the correct default values for fFlags (which prevents
any member modifications in the above methods).

This requires moving the definition of the disabled/write flags
out of the GrStencilSettings class definition's private section.
Note that the flags are renamed to avoid any confusion and
conflicts, i.e.:

  SkIsDisabled_Flag  -> SkIsDisabled_StencilFlag
  SkNotDisabled_Flag -> SkNotDisabled_StencilFlag
  ...
Review URL: https://codereview.appspot.com/5616051

git-svn-id: http://skia.googlecode.com/svn/trunk@3214 2bbb7eff-a529-9590-31e7-b0007b416f81