[packages/] remove packages which got moved to the telephony feed

 - libs/opal
 - libs/openh323
 - libs/ptlib
 - libs/pwlib

Signed-off-by: Jiri Slachta <slachta@cesnet.cz>
Signed-off-by: Mirko Vogt <mirko@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@37025 3c298f89-4303-0410-b956-a3cf2f4a3e73