Thanks to Harald, the git problems should be fixed now. Apparently OpenVZ by default limits the amount of sockets per instance to 1% of the global limit. Git is forking wildly, creating lots of orphaned sockets until it hits the limit.
Some people have reported problems when cloning the kernel tree, unfortunately these are so far unresolved. The kernel changes can alternatively be obtained in patch form from Patches.
Due to git object corruption in the asterisk git tree which prevented further resyncs with upstream SVN, I've replaced the tree by a fresh import of asterisk and chan_dect.
The history of chan_dect is retained, however the tree is not connected to the old one and needs to be recloned.
Since the libpcap developers have finally switched from CVS to git, I've replaced the outdated libpcap-dect tree by a new one based on the official tree from http://tcpdump.org. From now on the libpcap-dect tree will resync with upstream regulary.
The history of the old tree is not connected to the new one, therefore it needs to be re-cloned from scratch: