Bumping GLib Requirement for Pidgin3

[Ethan Blanton]

Matěj Cepl spake unto us the following wisdom:
> On 2015-06-18, 02:39 GMT, Ethan Blanton wrote:
> > 2.40 would include Ubuntu LTS, Debian Jessie, and RHEL 7.  I have no
> > problem with dropping support for long-term releases older than these.
> > By the time Pidgin 3.0 is out, they will all be thoroughly established
> > (Jessie is, to be fair, only a few days old!) and supported for many
> > years to come.
> 
> And when 3.0 is going to happen? Some birdie (or was it 
> a pigeon?) told me that perhaps Red Hat may (emphasize: may) 
> reintroduce pidgin back into RHEL 7 proper in some future minor 
> release.

When it's ready.  :-)  That said, we're pushing hard for it with this
GSoC.

Ethan