Mercurial 2.5.1

Closes #17720.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Vert-X  1.3.1

Closes #17721.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Grass: stil fails with clang 425.

Closes #17704.
irssi: allow opting out of perl support

Closes #15389.
irssi: fix syntax

Closes #17725.
rbenv: idiomatic directory paths

Closes #17722.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>