glsl: Make use of new _mesa_glsl_parse_state::check_version() function.

glsl: Make use of new _mesa_glsl_parse_state::check_version() function.

Previous to this patch, we were not very consistent about the errors
we generate when a shader tried to use a feature that is prohibited in
the current GLSL version.  Some error messages failed to mention the
GLSL version currently in use (or did so inaccurately), and some error
messages failed to mention the first GLSL version in which the given
feature is allowed.

This patch reworks all of the error checks to use the check_version()
function, which produces error messages in a standard form
(approximately "$FEATURE forbidden in $CURRENT_GLSL_VERSION
($REQUIRED_GLSL_VERSION required).").

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Carl Worth <cworth@cworth.org>