CONFIGURE: fix configure when gtk+ is not installed

AM_PATH_GTK_2_0 would be an undefined macro then
CONFIGURE: don't enable gconf schemas when gtk is disabled

This is nitpicky, since we could assume the user wants gconf schema if
gconftool-2 is available. However this can be a wrong assumption.
CONFIGURE: allow to pass specific python version

This is useful if distros support installing multiple python versions
in parallel such as: 2.5, 2.6, 2.7.
For python3.* we will get syntax error during the imports, so the checks
will successfully disable it.
It defaults to python2.
MAKE: don't include icons and desktop file for non-gtk builds
MAKE: install hexchat-plugin.h header if plugins are enabled
Cosmetics
Add missing include
Another missing include..
Last one
Get rid of installer skinning
Nuke Lua and Tcl
Remove another bunch of obsolete junk
Tabulation with spaces is annoying!
Remove old stuff, some preparation for soon-to-be-released Perl 5.18
Last cjstyles remnants
Remove Tcl junk, cosmetics
use proper table size
Merge pull request #484 from Phr33d0m/master

A few fixes on the *nix build system
add missing fi
Fix detecting python3