glcpp: Check version_resolved in the proper place.

glcpp: Check version_resolved in the proper place.

The check was in the wrong place, such that if a shader incorrectly put
a preprocessor token before the #version declaration, the version would
be resolved twice, leading to a segmentation fault when attempting to
redefine the __VERSION__ macro.

 #extension GL_ARB_sample_shading: require
 #version 130
 void main() {}

Also, rename glcpp_parser_resolve_version to
             glcpp_parser_resolve_implicit_version to avoid confusion.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>