svlog: ty: Hash/compare by ptr, fix perf
svlog: ty: Hash/compare by ptr, fix perf

Improve performance of the new types by hashing/comparing them by
pointer, since interning causes identical types to have identical
pointers anyway.

Fixes #183.

fabianschuiki/moore,fabianschuiki/moore,fabianschuiki/moore,fabianschuiki/moore,fabianschuiki/moore