Avoid const-time modulo in DSA verification
Avoid const-time modulo in DSA verification

It has a substantial perf hit and is not necessary. It may not
be really necessary for signatures either but leave that as it,
with a comment explaining.

randombit/botan,webmaster128/botan,webmaster128/botan,randombit/botan,webmaster128/botan,webmaster128/botan,randombit/botan,randombit/botan,randombit/botan,webmaster128/botan