pgsql: Fix crash on compiling a regular expression with more than 32k c

Fix crash on compiling a regular expression with more than 32k colors.

Throw an error instead.

Backpatch to all supported branches.

Branch
------
REL9_0_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/aae32bad9e3031fc440e9f2b6acd9a6170ad13be

Modified Files
--------------
src/backend/regex/regc_color.c |    8 ++++++++
src/include/regex/regerrs.h    |    4 ++++
src/include/regex/regex.h      |    1 +
src/include/regex/regguts.h    |    1 +
4 files changed, 14 insertions(+), 0 deletions(-)