Update irrtoolset5 to version 5.1.2.

Pkgsrc changes:
* Project moved to github, follow suit.
* Use the pre-configure target to run the required autotools
* Remove ancient GCC_REQD+=3.0
* Add use of more autotools
* Fix up PLIST with share/doc/irrtoolset/ files.

Upstream changes:

New Features
* initial support for IOS XR in rtconfig
* IOS support for peer templates (-cisco_peer_templates)
* support of community.delete on Cisco IOS
* implement importPeerGroup for JUNOS

Bug Fixes
* better asn32 support on JUNOS
* fix JUNOS output so it can be deployed using "load replace" (-junos_replace)
* several toolchain bugfixes (bison 2.x, gcc)
* workaround for compiler optimisation bug in gcc6
* permit community values starting with 0:
* updates for autotools

Other Notes
* Solaris no longer formally supported
* delete bugs/, contrib/ and tests/ directories
* added Travis CI support

We'd like to thank ISC for their continued support and the small
but important army of contributors who made this release possible.

(he)