Add two new gl_function methods. dispatch_name returns the name of

Add two new gl_function methods.  dispatch_name returns the name of
the true static dispatch name (either the glFooBar name or the
gl_dispatch_stub_XXX name).  static_name returns the name of the
static function for a specific alias of a GL function.

Adding (and using) these two functions corrects some problems in the
generated code related to functions with multiple aliases where some
of the aliases have true static dispatch functions and some don't.  I
have verified that everything under progs, except xdemos/xdemo,
correctly link.  I did this by doing 'make linux-dri-x86-64
PROGRAM_DIRS="demos redbook samples xdemos tests"'.