Specifically, make GLSL link error messages more specific and output
only information relevant to the error.
Also change type printing to more closely reflect GLSL syntax. This
is the default for link error messages, but must me enabled with the
new option --enhanced-msgs for compilation error messages.
Also with --enhanced-msgs, only emit one error message per source
line.
* Fixes#2005
Allow multiple units in a stage to have push_constants as long
as the blocks match.
Requires #2006 to be fixed to be functional.
* tweaks to #2005 fix after some testing
* add unit tests for push constants across multiple compilation units
For #2005
* update reference output for tests that fail validation
* fix uninitialized result.validationResult