Changes for reduced Guile distribution: one configure script,

Changes for reduced Guile distribution: one configure script,
no plugins.
* configure.in: Merged the old text from qt/configure.in and
libguile/configure.in; Tom Tromey says automake only wants one
configure.in script.  This seems fishy, but...
* Makefile.am: List the subdirectories explicitly; no more PLUGIN
gubbish.
* acconfig.h, acinclude.m4: Moved here from libguile, since
libguile's configure script lives here now.
* AUTHORS, INSTALL, README: Updated.
* Makefile.in, aclocal.m4 configure: Regenerated.  Just like
amputated amphibian limbs.