glsl: add extra pp tokens workaround and enable for CoR
The CTS now tests to make sure these are not allowed. However, previously drivers (including Mesa) would allow them to exist and just issue a warning. Some old applications such as Champions of Regnum seem to depend on this.
Closes: #422 (closed)
Fixes: 43047384 ("glsl/glcpp: Promote "extra token at end of directive" from warning to error")