i965 gs: Move vue_map to brw_gs_compile.

i965 gs: Move vue_map to brw_gs_compile.

This patch stores the geometry shader VUE map from a local variable in
compile_gs_prog() to a field in the brw_gs_compile struct, so that it
will be available while compiling the geometry shader.  This is
necessary in order to support transform feedback on Gen6, because the
Gen6 geometry shader code that supports transform feedback needs to be
able to inspect the VUE map in order to find the correct vertex data
to output.

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