Cast uid/gid proxies to int for Python 3.4.

See http://hg.python.org/cpython/rev/f871f8662509.
man/make.conf.5: Document shlex a bit, bug 309941
man/portage.5: Add notes about order, bug #388781
validate_desktop_entry: handle NotShowIn Pantheon

This will fix bug #480586.
vartree.py: Add link for collisions, bug #449918

Link to <http://wiki.gentoo.org/wiki/Knowledge_Base:Blockers> on
file collisions.