Character classes

Added most of an implementation of compact character classes, for use
in the regexp compiler.

[Christian Plesner Hansen, 2008-10-30 08:36:19]

Here's my work so far on character classes.  Bit-orama!

[Lasse Reichstein, 2008-10-30 10:28:42]

LGTM

http://codereview.chromium.org/8732/diff/1/3
File src/jsregexp.cc (right):

http://codereview.chromium.org/8732/diff/1/3#newcode1019
Line 1019: left->InitializeFieldFrom(boundaries.SubVector(0, i));
Try to read some more first, and see if more ranges fit into the same field.

http://codereview.chromium.org/8732/diff/1/3#newcode1023
Line 1023: *left = *this;
As discussed, the segments won't necessarily be disjoint if the next range are
in the same segment as the previous one.

http://codereview.chromium.org/8732/diff/1/4
File src/jsregexp.h (right):

http://codereview.chromium.org/8732/diff/1/4#newcode193
Line 193: static const int kFieldSegmentWidth = kCharSize -
kFieldSegmentIndexWidth;
Isn't this the field width, not the segment width?
(It's used to compute the kFieldMax).

http://codereview.chromium.org/8732/diff/1/4#newcode216
Line 216: } u_union;
Slightly confusing name to have for a struct (especially inside a union). Can't
think of more appropriate one, though.