Log Message:
pcre2: update to 10.33.

Version 10.33-RC1 16-April-2019
-------------------------------

Yet more bugfixes, tidies, and a few enhancements, summarized here (see
ChangeLog for the full list):

1. Callouts from pcre2_substitute() are now available.

2. The POSIX functions are now all called pcre2_regcomp() etc., with wrapper
functions that use the standard POSIX names. However, in pcre2posix.h the POSIX
names are defined as macros. This should help avoid linking with the wrong
library in some environments, while still exporting the POSIX names for
pre-existing programs that use them.

3. Some new options:

   (a) PCRE2_EXTRA_ESCAPED_CR_IS_LF makes \r behave as \n.

   (b) PCRE2_EXTRA_ALT_BSUX enables support for ECMAScript 6's \u{hh...}
       construct.

   (c) PCRE2_COPY_MATCHED_SUBJECT causes a copy of a matched subject to be
       made, instead of just remembering a pointer.

4. Some new Perl features:

   (a) Perl 5.28's experimental alphabetic names for atomic groups and
       lookaround assertions, for example, (*pla:...) and (*atomic:...).

   (b) The new Perl "script run" features (*script_run:...) and
       (*atomic_script_run:...) aka (*sr:...) and (*asr:...).

   (c) When PCRE2_UTF is set, allow non-ASCII letters and decimal digits in
       capture group names.

5. --disable-percent-zt disables the use of %zu and %td in formatting strings
in pcre2test. They were already automatically disabled for VC and older C
compilers.

6. Some changes related to callouts in pcre2grep:

   (a) Support for running an external program under VMS has been added, in
       addition to Windows and fork() support.

   (b) --disable-pcre2grep-callout-fork restricts the callout support in
       to the inbuilt echo facility.