glsl/parser: Move anonymous struct name handling to the parser

glsl/parser: Move anonymous struct name handling to the parser

There are two callers of the constructor, and they are right next to
each other.  Move the "#anon_struct" name handling to the parser so that
the conditional can be removed.

I've also deleted part of the comment (about the memory leak) because I
don't think it's quite accurate or relevant.

   text	   data	    bss	    dec	    hex	filename
8310399	 269336	 294072	8873807	 87674f	32-bit i965_dri.so before
8310339	 269336	 294072	8873747	 876713	32-bit i965_dri.so after
7845611	 346552	 420592	8612755	 836b93	64-bit i965_dri.so before
7845579	 346552	 420592	8612723	 836b73	64-bit i965_dri.so after

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>