Almost no OSes (except freebsd) allow i786 as a machine
variant in the toplevel configure file.

This patch allows them to accept the reasonable i[3-9]86
which is already used in some portions of the tree.

Bootstrapped GCC with --host=i786-pc-cygwin.  No
regressions.

After the corresponding obvious changes to binutils
directories which is being submitted seperately.  I also
configured, make and make -k check binutils on both
i686-pc-cygwin & i786-pc-cygwin with no regressions.

Kelley Cook <no CVSwrite privledges>