sr.ht/hg-evolve: bump pkgrel

Update mercurial and hg-evolve

Mercurial package is updated with the latest edge upstream to
install mercurial 5.1.2 with py3. Evolve is updated to 9.2.1
and also installs with py3.

Bump pkgrel on mercurial & hg-evolve

Add mercurial evolve package, make it a dependency of hgsrht