pgsql: Update: > * Allow the creation of indexes with mixed

Log Message:
-----------
Update:

* Allow the creation of indexes with mixed ascending/descending
specifiers

This is possible now by creating an operator class with reversed sort
operators. One complexity is that NULLs would then appear at the start
of the result set, and this might affect certain sort types, like
merge join.

Modified Files:
--------------
pgsql/doc:
TODO (r1.1788 -> r1.1789)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1788&r2=1.1789)
pgsql/doc/src/FAQ:
TODO.html (r1.292 -> r1.293)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.292&r2=1.293)