mesa/extensions: Replace extension::api_set with ::version

mesa/extensions: Replace extension::api_set with ::version

The api_set field has no users outside of _mesa_extension_supported().
Remove it and allow the version field to take its place.

The brunt of the transformation was performed with the following vim commands:
s/\(GL [^,]\+\),\s*\d*,\s*\d*\(,\s*\d*\)\(,\s*\d*\)/\1, GLL, GLC\2\3/g
s/\(GLL [^,]\+\)\,\s*\d*/\1, GLL/g
s/\(GLC [^,]\+\)\(,\s*\d*\),\s*\d*\(,\s*\d*\)\(,\s*\d*\)/\1\2, GLC\3\4/g
s/\( ES1[^,]*\)\(,\s*\(\w\|\d\)\+\)\(,\s*\(\w\|\d\)\+\),\s*\d*/\1\2\4, ES1/g
s/\( ES2[^,]*\)\(,\s*\(\w\|\d\)\+\)\(,\s*\(\w\|\d\)\+\)\(,\s*\(\w\|\d\)\+\),\s*\d*/\1\2\4\6, ES2/g

Signed-off-by: Nanley Chery <nanley.g.chery@intel.com>
Reviewed-by: Chad Versace <chad.versace@intel.com>