pgsql: Remove separate strdup.h header file; it's redundant with port.h.

Log Message:
-----------
Remove separate strdup.h header file; it's redundant with port.h.

Modified Files:
--------------
pgsql/src/bin/pg_dump:
common.c (r1.92 -> r1.93)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/common.c.diff?r1=1.92&r2=1.93)
pg_backup_db.c (r1.73 -> r1.74)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_db.c.diff?r1=1.73&r2=1.74)
pg_dump.c (r1.448 -> r1.449)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c.diff?r1=1.448&r2=1.449)
pg_dumpall.c (r1.81 -> r1.82)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dumpall.c.diff?r1=1.81&r2=1.82)
pg_restore.c (r1.80 -> r1.81)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_restore.c.diff?r1=1.80&r2=1.81)
pgsql/src/bin/psql:
common.c (r1.128 -> r1.129)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/common.c.diff?r1=1.128&r2=1.129)
pgsql/src/interfaces/libpq:
fe-connect.c (r1.335 -> r1.336)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-connect.c.diff?r1=1.335&r2=1.336)
fe-secure.c (r1.86 -> r1.87)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-secure.c.diff?r1=1.86&r2=1.87)
pgsql/src/port:
strdup.c (r1.11 -> r1.12)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/port/strdup.c.diff?r1=1.11&r2=1.12)

Removed Files:
-------------
pgsql/src/include:
strdup.h
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/strdup.h)