* Makefile.in: auto-host.h renamed from auto-config.h. All references
changed.
(distclean): Remove auto-build.h too.
* configure.in: Rename host autoconf generated file to auto-host.h.
If host != build, then run autoconf to generate auto-build.h for
the build machine and include it in build_xm_files.
Check for wait.h and sys/wait.h.