[patch] Adding boost as dependence

Guys,

Current AbiWord's trunk dependes of boost to compile.
So, I'm adding boost as dep in AbiCore, using the current easy way to
check for it.
To clarify, I'm moving ax_boost_base.m4 from abiword/plugins/collab/
to abiword and removeing boost as dep in AbiCollab and OpenXML
plugins.

About the version of boost to use, I was looking for versions that are
being used in some distros/systems and we have:
- Gentoo - 1.42.0
- Fedora - 1.44.0
- Arch Linux - 1.46.0
- Debian (stable) - 1.42.0
- Ubuntu (maverick) - 1.42.0
- MacOS (using MacPorts) - 1.45.0

As I build with 1.40.0 without errors, I'm checking for it.

Could someone review and apply? uwog?

Best Regards,

-- 
Fabiano Fidêncio