In commit 30fd43d7f3, unescape was
simplified significantly, but the new version failed to NULL terminate
the resulting string.
This causes bad behavior in various utilities, for example tr:
Broken:
$ echo b2 | tr '\142' '\143'
c3
Fixed:
$ echo b2 | tr '\142' '\143'
c2
This bug breaks libtool's usage of tr, causing gcc to fail to build with
sbase.
Yeah well, the old topic. POSIX allows \0123 and \123 octals in
different tools, in printf, depending on %b or other things.
We'll just keep it simple and just allow 4 digits. the 0 does not make
a difference anyway.
