Introduce AttribArray, a code generator for pseudo-type attrib_list.

Also use it for glXCreateConfigAttribsARB, which gives the expected
correct dumps in qapitrace and glretrace dump.
Nothing needs to change in dump code because it just reads whatever
types were written during tracing. Writing different types into
different array elements is allowed by the format, and it turns out
that even older versions of apitrace will correctly display dumps
created with this patch.