Log Message:
Update to 2.12:

* Noteworthy changes in release 2.12 (2012-03-19) [stable]
- Cleanup license headers.
- build: Update gnulib files.
- Corrected DER decoding issue (reported by Matthew Hall).
  Added self check to detect the problem, see tests/Test_overflow.c.
  This problem can lead to at least remotely triggered crashes, see
  further analysis on the libtasn1 mailing list.