Remove unused HAVE_* symbols for functions.

Remove unused HAVE_* symbols for functions.

* configure.in (AC_CHECK_FUNCS): Remove XSetWMProtocols,
getdomainname, mblen (twice), mbrlen (twice), mbsinit, ualarm,
getsockopt, setsockopt, mremap, mempcpy.
* admin/CPP-DEFINES (HAVE_GETDOMAINNAME): Remove.
* msdos/sed2v2.inp (HAVE_MBLEN): Remove.
* msdos/sed2x.inp (HAVE_XSETWMPROTOCOLS): Remove.
* nt/config.nt (HAVE_GETDOMAINNAME, HAVE_XSETWMPROTOCOLS)
(HAVE_GETSOCKOPT, HAVE_SETSOCKOPT): Remove; not needed.
* src/s/ms-w32.h (HAVE_GETDOMAINNAME): Remove; not needed.