Removing support for Emacs unexec from Glibc

The TeX implementation is much like the proposed approach of making a big data table out of what has been loaded in temacs, although that's less special in Pascal (what TeX is written in) than C. In Pascal, you can't have storage which can be cast between pointers and non-pointers, so TeX pretty much doesn't use pointers and instead has indexes into a large integer array; dumping that array and loading it into a different process isn't nearly as messy as trying to save a C heap with pointers or transforming a C heap into an array without pointers.