Sync our regex code with upstream changes since last time we did this,
which was Tcl 8.5.0 (see commit df1e965e).

There are no functional changes here; the main point is just to lay down
a commit-log marker that somebody has looked at this recently, and to do
what we can to keep the two codebases comparable.

This involves getting the character classification and case-folding
functions in the regex library to use the collations infrastructure.
Most of this work had been done already in connection with the upper/lower
and LIKE logic, so it was a simple matter of transposition.

While at it, split out these functions into a separate source file
regc_pg_locale.c, so that they can be correctly labeled with the Postgres
project's license rather than the Scriptics license.  These functions are
100% Postgres-written code whereas what remains in regc_locale.c is still
mostly not ours, so lumping them both under the same copyright notice was
getting more and more misleading.

from "clang".  The VERR changes make an assignment unconditional, which is
probably easier to read/understand anyway, and one can hardly argue that
it's worth shaving cycles off the case of reporting another error when
one has already been detected.  The INSIST change limits where that macro
can be used, but not in a way that creates a problem for any existing call.

matching before recursing instead of after.  The DFA match eliminates
unworkable midpoint choices a lot faster than the recursive check, in most
cases, so doing it first can speed things up; particularly in pathological
cases such as recently exhibited by Michael Glaesemann.

In addition, apply some cosmetic changes that were applied upstream (in the
Tcl project) at the same time, in order to sync with upstream version 1.15
of regexec.c.

Upstream apparently intends to backpatch this, so I will too.  The
pathological behavior could be unpleasant if encountered in the field,
which seems to justify any risk of introducing new bugs.

Tom Lane, reviewed by Donal K. Fellows of Tcl project

The specification of this function is as follows.

regexp_replace(source text, pattern text, replacement text, [flags
text])
returns text

Replace string that matches to regular expression in source text to
replacement text.

 - pattern is regular expression pattern.
 - replacement is replace string that can use '\1'-'\9', and '\&'.
    '\1'-'\9': back reference to the n'th subexpression.
    '\&'     : entire matched string.
 - flags can use the following values:
    g: global (replace all)
    i: ignore case
    When the flags is not specified, case sensitive, replace the first
    instance only.

Atsushi Ogawa

$Header: -> $PostgreSQL Changes ...

(extracted from Tcl 8.4.1 release, as Henry still hasn't got round to
making it a separate library).  This solves a performance problem for
multibyte, as well as upgrading our regexp support to match recent Tcl
and nearly match recent Perl.

postgres.h or c.h includes a system header (such as stdio.h or
stdlib.h), there's no need to specifically include it in any of the .c
files in the backend.

Neil Conway

Implement SQL99 SIMILAR TO as a synonym for our existing operator "~".
Implement SQL99 regular expression SUBSTRING(string FROM pat FOR escape).
 Extend the definition to make the FOR clause optional.
 Define textregexsubstr() to actually implement this feature.
Update the regression test to include these new string features.
 All tests pass.
Rename the regular expression support routines from "pg95_xxx" to "pg_xxx".
Define CREATE CHARACTER SET in the parser per SQL99. No implementation yet.

tests pass.

definitions from K&R to ANSI C style, and fix broken assumption that
int and long are the same datatype.  This repairs problems observed
on Alpha with regexps having between 32 and 63 states.

\d? results in one query. Add \d? field search feature.  Rename MB
to MULTIBYTE.

Included are patches intended for allowing PostgreSQL to handle
multi-byte charachter sets such as EUC(Extende Unix Code), Unicode and
Mule internal code. With the MB patch you can use multi-byte character
sets in regexp and LIKE. The encoding system chosen is determined at
the compile time.

To enable the MB extension, you need to define a variable "MB" in
Makefile.global or in Makefile.custom. For further information please
take a look at README.mb under doc directory.

(Note that unlike "jp patch" I do not use modified GNU regexp any
more. I changed Henry Spencer's regexp coming with PostgreSQL.)

Another PGINDENT run that changes variable indenting and case label indenting.  Also static variable indenting.

ppl are seeing with v2.0