* libguile/bdw-gc.h: Remove a needless compatibility hack.
* libguile/gc-inline.h: New file, implementing thread-local freelists
providing faster allocation if we already have a scm_i_thread*
pointer. Based on gc_inline.h from libgc.
* libguile/threads.h (scm_i_thread): Add freelists here.
* libguile/threads.c (guilify_self_1, guilify_self_2): Initialize
freelists.
* libguile/vm.c: Include gc-inline.h.
* libguile/vm-engine.c: Rename current_thread to thread. Use
scm_inline_cons instead of scm_cons, scm_inline_cell instead of
scm_cell, and scm_inline_words instead of words.
