Remove generated and auto-installed files from the distro.

* Makefile.in, aclocal.m4, configure, depcomp, install-sh,
  missing, common/Makefile.in, host/Makefile.in,
  lazycat-daemon/Makefile.in, proxies/Makefile.in, ui/Makefile.in:
  Remove.
configure.ac: Improve check for Guile modules.

* configure.ac: Improve check for Guile modules.
* INSTALL: Update.
configure.ac: Set `AC_CONFIG_AUX_DIR'.