[Mesa-dev] RFC initial KHR_no_error support

[Timothy Arceri]

This series adds some initial support for the KHR_no_error.

For now it can only be enabled with the MESA_NO_ERROR environment
variable. To start with I've added support to some of the api
calls that were taking a long time (or where caled often) in 
the Civ6 benchmark.

I haven't been able to measure much of an impact from these
changes in Civ6 (most cpu use tends to be in the st rather than
core Mesa for that benchmark), but the series is getting large
so I thought I'd send it out and start getting feedback.

I considered the suggestiong of using a different dispatch when
no error is enabled but that seemed like it would lead to a bunch
of duplication and mantance issues. For now I've opted to refactor
the code and insert a check for no_error at the highest level
possible. I think it has turned out nicely so far.