* src/bdd.h, src/bvec.h, src/fdd.h: Declare all exported
symbols using BUDDY_API, a new macro that sets visibility=default.
* src/Makefile.am: Compile with -fvisibility=hidden by default,
and compile the C++ part with -fvisibility-inlines-hidden as well.
This avoids a library call to bdd_addref or bdd_delref.
* src/kernel.c (bdd_delref_nc, bdd_addref_nc): New function,
that work only on BDD that are not constant.
* src/cpext.cxx (bdd::operator=): Move...
* src/bdd.hh (bdd::operator=): ... here.
(bdd::bdd, bdd::~bdd, bdd::operator=): Inline the "is bdd constant"
check and call bdd_delref_nc/bdd_addref_nc only otherwise.
Tag functions with attributes pure, const, or noreturn.
* src/bdd.h (__purefn, __constfn, __noreturnfn): Define
new macros.
* src/bdd.h, src/bddio.c, src/bvec.h, src/imatrix.h: Use them
to tag many functions as suggested by -Wsuggest-attribute=pure,
-Wsuggest-attribute=const, -Wsuggest-attribute=noreturn.
Inline bdd_addref() and bdd_delref() to speedup BDD operations.
* src/kernel.c, src/kernel.h (bdd_addref, bdd_delref): Move these
functions and there associated global variables...
* src/bdd.c (bdd_error): ... and this function ...
* src/bdd.h (bdd_addref, bdd_delref, bdd_error): ...here so that
they can be inlined.
bdd_uniquecomp, bdd_appexcomp, bdd_appallcomp,
bdd_appunicomp): Declare for C and C++.
* src/bddop.c (CACHEID_EXISTC, CACHEID_FORALLC,
CACHEID_UNIQUEC, CACHEID_APPEXC, CACHEID_APPALC,
CACHEID_APPUNCC): New macros.
(quatvarsetcomp): New variables.
(varset2vartable): Take a second argument to indicate negation,
set quatvarsetcomp.
(INVARSET): Honor quatvarsetcomp.
(quantify): New function, extracted from bdd_exist, bdd_forall,
and bdd_appunicomp.
(bdd_exist, bdd_forall, bdd_appunicomp): Use quantify.
(bdd_existcomp, bdd_forallcomp, bdd_appunicompcomp): New functions.
(appquantify): New function, extracted from bdd_appex, bdd_appall,
and bdd_appuni.
(bdd_appex, bdd_appall, bdd_appuni): Use appquantify.
(bdd_appexcomp, bdd_appallcomp, bdd_appunicomp): New functions.
* src/bddop.c (bdd_support): Return bddtrue when the support
is empty, because variable sets are conjunctions.
