glsl: glcpp: Move handling of #line directives from lexer to parser.

glsl: glcpp: Move handling of #line directives from lexer to parser.

The GLSL specification requires that #line directives be interpreted
after macro expansion. Our existing implementation of #line macros in
the lexer prevents conformance on this point.

Moving the handling of #line from the lexer to the parser gives us the
macro expansion we need. An additional benefit is that the
preprocessor also now supports comments on the same line as #line
directives.

Finally, the preprocessor now emits the (fully-macro-expanded) #line
directives into the output. This allows the full GLSL compiler to also
see and interpret these directives so it can also generate correct
line numbers in error messages.

Signed-off-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>