glsl/glcpp: Fix #pragma to not over-increment the line-number count

glsl/glcpp: Fix #pragma to not over-increment the line-number count

Previously, the #pragma directive was swallowing an entire line, (including
the final newline). At that time it was appropriate for it to increment the
line count.

More recently, our handling of #pragma changed to not include the newline. But
the code to increment yylineno stuck around. This was causing __LINE__ to be
increased by one more than desired for every #pragma.

Remove the bogus, extra increment, and add a test for this case.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>