asterisk: Update to 1.8.13.0.

The 1.4 branch of asterisk does not build with the new flex and bison.
Also, the 1.4 branch was EOL'ed April 2012. The 1.8 branch has long
term support until 2015.

This patch also update chan_capi to the most recent version (HEAD),
as this is the only one that compiles with asterisk 1.8.

Asterisk 1.8 ships addons as part of the main tarball.
Asterisk 1.8 has no build in mp3 support anymore, mp3 libs need to be
downloaded seperatly via svn
(see asterisk-1.8.13.0/contrib/scripts/get_mp3_source.sh).
This patch DOES NOT include mp3 support.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>