Jakub has recently implemented some of the Dwarf3 CFA value
expressions: http://sourceware.org/ml/binutils/2006-03/msg00009.html
http://sourceware.org/ml/binutils/2006-03/msg00043.html

Support in the GCC unwinder is in the works (or maybe already
contributed and I couldn't find it :-), but GDB is still missing
support for such encodings.  Without this patch, when it encounters
them, it complains loudly and fails to issue backtraces, as with the
testcases in the patch that follows.

This patch introduces support for the new encodings.  Tested on
amd64-linux-gnu.  Ok to install?