pgsql-server: Allow libpgport to call memory allocation routines even

Log Message:
-----------
Allow libpgport to call memory allocation routines even though
CurrentMemoryContext is DLLIMPORT on Win32. Work around that by
creating stubs in the backend for palloc/pstrdup.

Also fix pg_dumpall to do proper quoting on Win32.

Modified Files:
--------------
pgsql-server/src/backend/utils/mmgr:
mcxt.c (r1.46 -> r1.47)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/mmgr/mcxt.c.diff?r1=1.46&r2=1.47)
pgsql-server/src/bin/pg_dump:
pg_dumpall.c (r1.46 -> r1.47)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/bin/pg_dump/pg_dumpall.c.diff?r1=1.46&r2=1.47)
pgsql-server/src/include:
port.h (r1.49 -> r1.50)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/port.h.diff?r1=1.49&r2=1.50)
pgsql-server/src/include/utils:
palloc.h (r1.27 -> r1.28)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/utils/palloc.h.diff?r1=1.27&r2=1.28)
pgsql-server/src/port:
dirmod.c (r1.17 -> r1.18)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/port/dirmod.c.diff?r1=1.17&r2=1.18)