Call for help: moving manpages to share/man

Ahoy there fellow porters!

portmgr@ is currently working on switching the directory into which
man pages are installed from "${PREFIX}/man" to "${PREFIX}/share/man".
It is quite a tedious process, as you might imagine. More than that,
changing the default for a given build system instantly breaks all
ports that use it, which means that this task can't be done
incrementally in the main branch.

I've created a branch [1] in my own fork that switches mandir for the
autotools build system and am inviting everyone to collaborate on
that, until all the fallout is fixed. I'm asking port maintainers to
check if they have ports with the "GNU_CONFIGURE=yes" knob, as these
are most likely broken by the switch. Moin kindly prepared a list of
affected ports along with their maintainers (thanks Moin!) [2]

In the most simple case you'll only need to change the pkg-plist, as I
did in this example commit [3]. Make sure to bump PORTREVISION as
we're altering the package's contents by this change. Also put the
"Approved by: portmgr (blanket)" tag in the commit message, as the
whole initiative was approved by the portmgr@ group.

If you want to collaborate either create a pull request on GH against
my branch or just send me a git format-patch output for your change.

Thanks beforehand to everyone going to help!

[1] https://github.com/arrowd/freebsd-ports/tree/autotools-mandir
[2] http://arrowd.name/manprefix-fail.maintainer.txt
[3] https://github.com/arrowd/freebsd-ports/commit/cc288e9b742cd54640e06737334dd57d88d45f6d