This includes removing tabs after periods in C comments, which was
applied to back branches, so this change should not effect backpatching.

Specifically, on-stack memset() might be removed, so:

	* Replace memset() with px_memset()
	* Add px_memset to copy_crlf()
	* Add px_memset to pgp-s2k.c

Patch by Marko Kreen

Report by PVS-Studio

Backpatch through 8.4.

pgp.h used to require including mbuf.h and px.h first.  Include those in
pgp.h, so that it can be used without prerequisites.  Remove mbuf.h
inclusions in .c files where mbuf.h features are not used
directly.  (px.h was always used.)

provided by Andrew.

be more wary about having a value for BYTE_ORDER, clean up randomly-
chosen ways of including Postgres core headers.
Marko Kreen and Tom Lane