i965: Dump shader source for linked shader programs.

i965: Dump shader source for linked shader programs.

We dump shader source in ir_to_mesa.cpp, and we dump linked programs here,
but we had no reference from the linked programs to their source.  This
was preventing improvement of shader-db to use linked shader programs
instead of individual shader files (which is bogus, because it means we
optimize out VS outputs, and don't interpolate FS inputs!)

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>