Reorder 9.3 release note items

Typo fix from David Fetter.
Adjust 9.3 release notes per request from Simon
9.3 release note fixes

Move commit_delay, fix Zoltan's name, and adjust range type histogram
text.
Remove 9.3 item about fixing DROP INDEX CONCURRENTLY

Already fixed in back branch.
9.3 release note adjustments per request from Andres Freund
In 9.3 release notes, split up items

Split log shipping speed improvement and fail-over speed improvement items.

Per request from Simon
doc: Fix syntax in example

LANGUAGE 'plpgsql' no longer works.  The single quotes need to be
removed.

Erwin Brandstetter
doc: Improve example formatting

Erwin Brandstetter