Aggregate `Makefile.am' files under `examples/'.

Aggregate `Makefile.am' files under `examples/'.

* configure.in: Don't produce `examples/*/Makefile'.

* examples/Makefile.am (SUBDIRS): Remove.
  (EXTRA_DIST, AM_CFLAGS, AM_LIBS): New.
  (box/box, box/box.o, box-module/box, box-module/box.o, libbox.la,
  box-dynamic/box.lo, libbox-module.la, box-dynamic-module/box.lo,
  installcheck, CLEANFILES, clean-local): New targets, aggregated from
  `Makefile.am' files formerly in sub-directories.

* examples/check.test: New file, aggregated from `check.test' files in
  sub-directories.