[Mesa-dev] Two more patches for glcpp conformance work

[Carl Worth]

I think that with these two, I've completed my recent goal to bring glcpp into
conformance with the latest Khronos GLES3 conformance tests. I'll be doing
some full test runs over the CTS tests to see if I've missed anything.

The first patch here is a fairly trivial thing, (make glcpp emit a blank line
for any empty "#pragma").

But the second patch is probably the least trivial piece of code in the entire
recent series. I had to muck around a bit in the open-coded
recursive-expansion code to fix the handling of macros that expand to include
"defined" operators. I couldn't find any way to do this inside the grammar
itself.

All the details are in the commit message and comments, so I won't say more
here. I just wanted to call attention to this patch as it may warrant a bit
more review than much of what I have written in the past couple of weeks.

-Carl