jhbuild update required

[Colin Walters <walters verbum org>]

Hi,

TL;DR: Run "git pull -r && make install" in your jhbuild checkouts.

The latest "systemmodules" work has landed in jhbuild; in the default
configuration where modulesets are fetched via HTTP, the new ones will
fail to parse with the old code.

The upside though is that "jhbuild sysdeps --install" now does a LOT
more.

For future jhbuild updates we'll try to either add a moduleset version
field that makes this error more obvious, or even better - teach jhbuild
how to auto-update itself.