[autoconf-conversion] Something to start with

[DJ Delorie]

> We've currently got libiberty, gas, and fastjar.  Any others in
> particular you would like to see in the first pass?

gcc builds build, host, and target foo.  It's probably the worst case
next to libiberty.

Do we have a warm and fuzzy about the 2.13/2.57 incompatibilities?  Do
we need to tweak the toplevel for them, or does it happen to just
work?