[Mesa-dev] glsl: New blob.c (in preparation for shader cache)

[Carl Worth]

Here are two patches that add some functions for serializing and
deserializing simple data structures, (integers of various sizes,
pointers, and strings).

This code will be used by my upcoming shader-cache work. I'm
submitting it here now because it is self-contained and documented, so
it should be ready to be reviewed now.

But it probably makes sense to wait to push this until I actually have
some reviewed code that uses it.

I want to thank Tapani for some similar code he wrote for his IR
serialization work. As attributed in the second patch below, I shared
some ideas directly from one of his patches.

-Carl