Replace regular expression package with Henry Spencer's latest version

(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.

src/include/regex/regcustom.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 1998, 1999 Henry Spencer.  All rights reserved.
+ * 
+ * Development of this software was funded, in part, by Cray Research Inc.,
+ * UUNET Communications Services Inc., Sun Microsystems Inc., and Scriptics
+ * Corporation, none of whom are responsible for the results.  The author
+ * thanks all of them. 
+ * 
+ * Redistribution and use in source and binary forms -- with or without
+ * modification -- are permitted for any purpose, provided that
+ * redistributions in source form retain this entire copyright notice and
+ * indicate the origin and nature of any modifications.
+ * 
+ * I'd appreciate being given credit for this package in the documentation
+ * of software which uses it, but that is not a requirement.
+ * 
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
+ * HENRY SPENCER BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $Id: regcustom.h,v 1.1 2003/02/05 17:41:32 tgl Exp $
+ */
+
+/* headers if any */
+#include "postgres.h"
+
+#include <ctype.h>
+#include <limits.h>
+
+#include "mb/pg_wchar.h"
+
+
+/* overrides for regguts.h definitions, if any */
+#define	FUNCPTR(name, args)	(*name) args
+#define	MALLOC(n)		malloc(n)
+#define	FREE(p)			free(VS(p))
+#define	REALLOC(p,n)		realloc(VS(p),n)
+
+/* internal character type and related */
+typedef pg_wchar chr;	/* the type itself */
+typedef unsigned uchr;		/* unsigned type that will hold a chr */
+typedef int celt;		/* type to hold chr, MCCE number, or NOCELT */
+#define	NOCELT	(-1)		/* celt value which is not valid chr or MCCE */
+#define	CHR(c)	((unsigned char) (c)) /* turn char literal into chr literal */
+#define	DIGITVAL(c)	((c)-'0')	/* turn chr digit into its value */
+#define	CHRBITS	32		/* bits in a chr; must not use sizeof */
+#define	CHR_MIN	0x00000000		/* smallest and largest chr; the value */
+#define	CHR_MAX	0xfffffffe		/*  CHR_MAX-CHR_MIN+1 should fit in uchr */
+
+/* functions operating on chr */
+#define	iscalnum(x)	pg_isalnum(x)
+#define	iscalpha(x)	pg_isalpha(x)
+#define	iscdigit(x)	pg_isdigit(x)
+#define	iscspace(x)	pg_isspace(x)
+
+/* and pick up the standard header */
+#include "regex.h"