* Makefile.in: add EXTRA_INCS

* Makefile.in: add EXTRA_INCS
* configure.in: if with-newlib, point to it for includes
rather than using the installed includes, for target builds.
If cygwin, override function list only for target builds.
* configure: regenerate
Note from DJ: I waited a week for gcc approval and got none, but
we need this patch for cygwin builds *now*.  I'll fix it later if
need be.