Makefile.autotools.in improvements

[Daniel Laird]

What do people think about adding
HOOK_POST_EXTRACT and HOOK_POST_CONFIGURE
targets, the problem with libxml2 highlighted that I can not stop it trying to do the ltmain.sh patch after an extract.  It then finds left over rubbish (*.rej) and rejects.
However if I had a HOOK_POST_EXTRACT target I could extract tarball and then delete rubbish and then let it do the ltmain.sh patching.

What do people think?
Daniel Laird