Cleanup plist
Add USES=alias to several ports

Alias is a new USES tool that allows DragonFly to masquerade as FreeBSD
by setting CFLAGS+= -D__FreeBSD__.  For some ports, this fixes the build
without the need for additional patches.

Approved by:	portmgr (bapt, blanket)
Cleanup plist
multimedia/mlt: add USES=alias plus ...

USES=alias allows the port to build on DragonFly without patches, but
only if --target-os=FreeBSD is also sent to the configure script.  This
is a no-op for FreeBSD (configure eventually sets target-os to FreeBSD
anyway).  USES=alias was covered by portmgr blanket.
- Fix format:
  - Add blank line
  - Remove trailing space
Add USES=alias to several ports

Alias is a new USES tool that allows DragonFly to masquerade as FreeBSD
by setting CFLAGS+= -D__FreeBSD__.  For some ports, this fixes the build
without the need for additional patches.

Approved by:	portmgr (bapt, blanket)