Add pkgng support

This is a preliminary support.
In order to use it, please add use_pkgng=yes to your portmasterrc
So far only portmaster -a has been tested
No need set -x
Fix typos in portmaster
Add -y to pkg delete and support pkg_create
Use pkg query in portmaster
Upgrade the portmaster patch to 3.10

While here make multiport working
Merge tag '3.10' into integrate-pkgng

Conflicts:
	portmaster
Fix a couple of issues with pkg invocation
Spell "use_pkgng" correctly
Convert some pkg info to pkg query

bapt@ suggested that pkg query is better suited for usage in scripts
Fix pkg info call

`pkg_info $port` is equivalent to `pkg info -f $port`.
Cleanup style

Make (almost) all checks of $use_pkgng use the same style.
Fix call to pkg info
Fix typo and indentation
Fix package name of installed port

While the old test would fail, `pkg info -e $port` would also accept
a port name without version, which would result in a message like:

===>>> Currently installed version: gmake

We have to explicitly assign to $upg_port name and version of the
package.
Merge tag '3.11' into integrate-pkgng
Update to portmaster 3.11

The new feature to preserve files across updates is yet to be
implemented.
Add check for existing port when about to expunge

While here, change the hardcoded "pkg_delete" in a message with the
correct tool name.
Fix deinstallation of stale ports

It's mostly a hack, it should be replaced by pkg autoremove as soon as
it works.
Fix listing of installed ports by categories

The logic had to be completely inverted, the loop had to be modified
to actually use the global variables, and, while I was here, I also
declared a couple of local variables and fixed style. Tududu.