some escaping bugs in SRE.

This patch includes test cases and documentation updates, as well as NEWS file
updates.

This patch also updates the sre modules so that they don't import the string
module, breaking direct circular imports.

* Factor constant expressions out of loops.
* Presize a list being grown to a known length.

Will backport to 2.2.

A small fix for bug #545855 and Greg Chapman's
addition of op code SRE_OP_MIN_REPEAT_ONE for
eliminating recursion on simple uses of pattern '*?' on a
long string.

backed out of broken minimal repeat patch from July

also fixed a couple of minor potential resource leaks in pattern_subx
(Guido had already fixed the big one)

and NEWS.  Bugfix candidate?  That's a dilemma for Anthony <wink>:  /F
did fix a longstanding bug here, but the fix can cause code to raise an
exception that previously worked by accident.

the error it really is (and always has been)

\g<x> group reference followed by a character escape

(also restructured a few things on the way to fixing #449000)

- take locale into account for word boundary anchors (#410271)
- restored 2.0's *? behaviour (#233283, #408936 and others)
- speed up re.sub/re.subn

- removed __all__ cruft from internal modules (sorry, skip)
- don't assume ASCII for string escapes (sorry, per)

also modified check_all function to suppress all warnings since they aren't
relevant to what this test is doing (allows quiet checking of regsub, for
instance)

compatibility patches.

-- added some more docstrings
-- fixed typo in scanner class (#125531)
-- the multiline flag (?m) should't affect the \Z operator (#127259)
-- fixed non-greedy backtracking bug (#123769, #127259)
-- added sre.DEBUG flag (currently dumps the parsed pattern structure)
-- fixed a couple of glitches in groupdict (the #126587 memory leak
   had already been fixed by AMK)

-- fixed negative lookbehind to work correctly at the beginning
of the target string (bug #117242)

-- improved syntax check; you can no longer refer to a group
inside itself (bug #110866)

character class.  Fix provided by Andrew Kuchling.  Closes bug
#116251.

first scan.  Closes bug #115040.

-- improved the SRE test harness: don't use asserts, test a few more
   things (including more boundary conditions)

"sre_parse.py missing '7' in DIGITS"

I fixed the a bug in the regression test harness...)

   (this should fix Sjoerd's xmllib problem)
-- added skip field to INFO header
-- changed compiler to generate charset INFO header
-- changed trace messages to support post-mortem analysis

-- added REPEAT_ONE operator
-- added ANY_ALL operator (used to represent "(?s).")

-- fixed literal check in branch operator
   (this broke test_tokenize, as reported by Mark Favas)
-- added REPEAT_ONE operator (still not enabled, though)
-- added some debugging stuff (maxlevel)

-- reverted REPEAT operator to use "repeat context" strategy
   (from 0.8.X), but done right this time.
-- got rid of backtracking stack; use nested SRE_MATCH calls
   instead (should probably put it back again in 0.9.9 ;-)
-- properly reset state in scanner mode
-- don't use aggressive inlining by default

 + added "regs" attribute
 + fixed "pos" and "endpos" attributes
 + reset "lastindex" and "lastgroup" in scanner methods
 + removed (?P#id) syntax; the "lastindex" and "lastgroup"
   attributes are now always set
 + removed string module dependencies in sre_parse
 + better debugging support in sre_parse
 + various tweaks to build under 1.5.2

- changed "group" operator to "groupref"

  the pattern must have a fixed width.

- got rid of array-module dependencies; the match pro-
  gram is now stored inside the pattern object, rather
  than in an extra string buffer.

- cleaned up a various of potential leaks, api abuses,
  and other minors in the engine module.

- use mal's new isalnum macro, rather than my own work-
  around.

- untabified test_sre.py.  seems like I removed a couple
  of trailing spaces in the process...