pgsql: Miscellaneous cleanup of regular-expression compiler.

Miscellaneous cleanup of regular-expression compiler.

Revert our previous addition of "all" flags to copyins() and copyouts();
they're no longer needed, and were never anything but an unsightly hack.

Improve a couple of infelicities in the REG_DEBUG code for dumping
the NFA data structure, including adding code to count the total
number of states and arcs.

Add a couple of missed error checks.

Add some more documentation in the README file, and some regression tests
illustrating cases that exceeded the state-count limit and/or took
unreasonable amounts of time before this set of patches.

Back-patch to all supported branches.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/afdfcd3f7617c9b7be5966d66ddabdc2e92eb99b

Modified Files
--------------
src/backend/regex/README            |   95 +++++++++++++++++++++++++++++++----
src/backend/regex/regc_nfa.c        |   55 +++++++-------------
src/backend/regex/regcomp.c         |   11 ++--
src/test/regress/expected/regex.out |   35 +++++++++++++
src/test/regress/sql/regex.sql      |   11 ++++
5 files changed, 153 insertions(+), 54 deletions(-)