[dev] wmii + libixp: minor fixes for builds

Hello,

while working on the updates to the OpenBSD ports of libixp and wmii I
hit some minor issues that needed to be fixed. The updated ports include
the necessary patches, but it would be great if those would be included
at the source, too.

wmii:
1. A shell variable in mk/dir.mk isn't escaped properly.
2. cmd/wmii/_util.c and cmd/wmii/main.c use functions defined in
<signal.h>, but include <sys/signal.h> only.
3. The build scripts still reference iconv although it isn't used in the
code anymore.

-> wmii-3.9.2-buildfix.diff

libixp:
1. Same error in mk/dir.mk as above.
2. libixp/server.c uses memset, but doesn't include <string.h>.
3. There's a typo in the license note.

-> libixp-0.5-buildfix.diff

Regards,
Oliver Klima