The TLS dispatch functions for x86-64 are fixed-size, just like on

The TLS dispatch functions for x86-64 are fixed-size, just like on
x86.  This means that the position of each dispatch function can be
calculated as (dispatch_offset * size_of_function) + glNewList.  This
allows us to not store the function pointers in glprocs_table_t.

This same optimization has been done for quite some time on x86.  We
could probably also do this for some cases of the SPARC dispatch as
well.