params.def (ggc-min-expand, [...]): New parameters.
* params.def (ggc-min-expand, ggc-min-heapsize): New parameters.
* doc/invoke.texi: Document them.
* ggc-page.c: Include params.h. Remove definitions of
GGC_MIN_EXPAND_FOR_GC, GGC_MIN_LAST_ALLOCATED. Replace
GGC_POISON with ENABLE_GC_CHECKING in ifdefs, delete #define.
(init_gcc): Don't set G.allocated_last_gc here.
(ggc_collect): Use PARAM_VALUE (GGC_MIN_HEAPSIZE) and
PARAM_VALUE (GGC_MIN_EXPAND) to decide whether or not to
perform collection.
* ggc-simple.c: Similarly.
* Makefile.in (ggc-common.o, ggc-simple.o): Add $(PARAMS_H) to
dependencies.