pgsql: Add ALTER ROLE ALL SET command

Add ALTER ROLE ALL SET command

This generalizes the existing ALTER ROLE ... SET and ALTER DATABASE
... SET functionality to allow creating settings that apply to all users
in all databases.

reviewed by Pavel Stehule

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/9475db3a4eb5876b364254886d2730db01e042fd

Modified Files
--------------
doc/src/sgml/ref/alter_role.sgml  |   27 ++++++++---
src/backend/commands/user.c       |   92 +++++++++++++++++++++++--------------
src/backend/parser/gram.y         |    8 +++
src/backend/utils/init/postinit.c |    1 +
src/backend/utils/misc/guc.c      |    3 +-
src/include/utils/guc.h           |    1 +
6 files changed, 90 insertions(+), 42 deletions(-)