glsl-syntax

Copperbox revision 2713.

The parser now works - it must never have been working when I abandoned it as I had to relax the distinction in the parser grammar between identifiers and field selectors - basically the lexer never knows what is a field selector so it has to class everything as an identifier.

The parser isn't going to be robust - I think GLSL code in the wild uses CPP which it obviously can't handle. Also I think the grammar for GLSL has changed vis void main () and void main (void) - as my parser is LALR, which is always a struggle to use, I'm not going to rush to make it handle errors and discrepancies.