rx.ops, bitmaps and memory leaks

[Leopold Toetsch]

Rx had some time ago (~0.0.6) a state structure rxinfo. AFAIK this was tossed for speed reasons, state is kept in registers now.
This has several impacts:
- regexen are not reentrant anymore (global intstack)
- they don't/can't manage their allocated resources like bitmaps

1) I would propose, that all ops, which work with bitmaps and rxstack have again a state structure.
(Reentrante regexen would probably need all the state there, but these could be separate ops as well)

2) For bitmaps I would provide a bitlist.c with functions for setting and testing bits. This bitlist would be based on list, so it should be fast enough and had no limits WRT unicode chars.

3) There are some global bitmaps like bitmaps of RX_WORDCHARS or RX_SPACECHARS containing all word or space chars respectively. These should probably go into the chartypes/ directory, currently they are usacii only.

Comments welcome,
leo