pgsql: Get rid of retail definitions of HAVE_STRDUP and HAVE_VSNPRINTF

Log Message:
-----------
Get rid of retail definitions of HAVE_STRDUP and HAVE_VSNPRINTF in
some of the Windows-only makefiles; the correct place to assert these
things is pg_config.h.win32. Per bug #2677.

Modified Files:
--------------
pgsql/src/bin/pg_config:
win32.mak (r1.7 -> r1.8)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_config/win32.mak.diff?r1=1.7&r2=1.8)
pgsql/src/bin/pg_dump:
win32.mak (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/win32.mak.diff?r1=1.4&r2=1.5)
pgsql/src/bin/psql:
bcc32.mak (r1.15 -> r1.16)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/bcc32.mak.diff?r1=1.15&r2=1.16)
win32.mak (r1.33 -> r1.34)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/win32.mak.diff?r1=1.33&r2=1.34)
pgsql/src/include:
pg_config.h.win32 (r1.35 -> r1.36)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/pg_config.h.win32.diff?r1=1.35&r2=1.36)
pgsql/src/interfaces/libpq:
bcc32.mak (r1.24 -> r1.25)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/bcc32.mak.diff?r1=1.24&r2=1.25)
win32.mak (r1.41 -> r1.42)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/win32.mak.diff?r1=1.41&r2=1.42)