Fix assertion violation and partial overlapping in remove_roots_subregion
(fix of commit
38d194a)
Issue #218 (bdwgc).
* mark_rts.c [USE_PROC_FOR_LIBRARIES] (GC_remove_roots_subregion):
Update comment; add assertion that b and e pointers are word-aligned;
handle also cases of partial overlapping with the existing roots;
call GC_rebuild_root_index() only when needed; update existing root
instead of removing old and adding new one (where possible); move
newly static added root to precede dynamic ones (if any); process all
static roots even if an intersection is already found.