Here is a release of the "old" UST branch, updating it to compile with
the newer liburcu >= 0.6.6.

Changelog:

2011-12-15 ust 0.16
* Use caa_unlikely, depend on liburcu >= 0.6.6
* usttrace: allow spaces in command-line arguments
* Fix tracepoint test with deprecated API
* Add powerpc64 host_cpu to configure.ac
* Mark __tp_cb_data as possibly unused for backward compat API
* Fix git URL