glsl: Add GLSL version query functions.

glsl: Add GLSL version query functions.

With the advent of GLSL 3.00 ES, the version checks we perform in the
GLSL compiler (to determine which language features are present) will
become more complicated.  To reduce the complexity, this patch adds
functions check_version() and is_version() to _mesa_glsl_parse_state.
These functions take two version numbers: a desktop GLSL version and a
GLSL ES version, and return a boolean indicating whether the GLSL
version being compiled is at least the required version.  So, for
example, is_version(130, 300) returns true if the GLSL version being
compiled is at least desktop GLSL 1.30 or GLSL 3.00.

The check_version() function additionally produces an error message if
the version check fails, informing the user of which GLSL version(s)
support the given feature.

[v2, idr]: Add PRINTFLIKE annotation to the new method.  The numbering of th
parameters is correct because GCC is silly.

[v3, idr]: Fix copy-and-paste error in the comment before
_mesa_glsl_parse_state::is_version.  Noticed by Ken.

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