explicitely requested (--with-included-buddy) or if there is
now stuitable version already installed.
* buddy/: New directory. Contains a patched version of BuDDy 2.2.
* m4/buddy.m4: Make sure the installed BuDDy supports bdd_mergepairs.
Honor --with-included-buddy and --without-included-buddy. Define
the BUDDY_LDFLAGS and BUDDY_CPPFLAGS output variables, and the
WITH_INCLUDED_BUDDY Automake conditional
* Makefile.am [WITH_INCLUDED_BUDDY] (MAYBE_SUBDIRS): New variable.
(SUBDIRS): Prepend $(MAYBE_SUBDIRS).
* src/Makefile.am (libspot_LDFLAGS): New variable.
* src/tgba/Makefile.am (AM_CPPFLAGS): Add $(BUDDY_CPPFLAGS).
* src/tgbaalgos/Makefile.am (AM_CPPFLAGS): Likewise.
* src/tgbatest/Makefile.am (AM_CPPFLAGS): Likewise.
