main: return two minor digits for ES shading language version

main: return two minor digits for ES shading language version

For OpenGL ES 3.0 spec, the minor number for SHADING_LANGUAGE_VERSION is always
two digits, matching the OpenGL ES Shading Language Specification release
number. For example, this query might return the string "3.00".

This patch fixes the following dEQP test:

   dEQP-GLES3.functional.state_query.string.shading_language_version

No piglit regression observed.

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>