Copyedit comments and documentation.

config/c-compiler.m4

contrib/pgstattuple/pgstatapprox.c

doc/src/sgml/install-windows.sgml

doc/src/sgml/release-9.3.sgml

doc/src/sgml/xml2.sgml

src/backend/executor/execParallel.c

src/backend/storage/buffer/README

src/backend/storage/buffer/bufmgr.c

src/backend/storage/freespace/freespace.c

src/backend/storage/ipc/procarray.c

src/backend/storage/lmgr/predicate.c

src/backend/storage/smgr/md.c

src/backend/utils/adt/timestamp.c

src/backend/utils/hash/dynahash.c

src/pl/plperl/plperl.c

src/test/perl/TestLib.pm

src/tools/valgrind.supp