Otherwise if you for example share root of libevent repository with some
vm (for example windows+cygwin) then if you try to build with configure
on host, and then on guest it will fail, so let's just ignore this since
autogen.sh is just for this -- cleaning all stuff.
Previously, our autogen.sh script wouldn't tell automake to update
older versions of its copied-in scripts, which would cause problems if
they got sufficiently out-of-date.
Apply patch from Trond Norbye with recommendations from Magne Mahre and Hannah Schroeter: make autogen.sh work on systems where /bin/sh is not bash.
svn:r444
