Optional dep on Boost.Locale for Azoth MuCommands

[Georg Rudoy]

Hi!

I've added an (optional) dependency on Boost.Locale in Azoth
MuCommands module for the issue http://dev.leechcraft.org/issues/1657

The dep is controlled by "USE_AZOTH_MUCOMMANDS_BOOST_LOCALE" use flag.
As LC depends on Boost anyway, this option is enabled by default. The
reason for the existence of this option is for merely optional pulling
of the Boost.Locale library binary (as it's not header-only).
It is recommended to be on.

--
Georg Rudoy