utilize stack member from base Error class
Merge pull request #1990 from inolen/errnoopt

utilize stack member from base Error class
Merge pull request #1972 from juj/gl__opts

GL cleanup and optimizations.
support exceptions using fastcomp
prevent calling run more than once; fixes #1992
Optimize GL emulation prepareClientAttributes. Fix issues where the slow path was not able to handle unaligned source data. Remove liveClientAttributes, which does not seem to be a win in profiles.