The ximagesink and xvimagesink plugins do not build under FreeBSD.  They include
the sys/ipc.h and sys/shm.h header files, but these need sys/types.h to be
included as a prerequisite to work; and this must be done manually.

Building a simple test case program that only includes those two files shows it:

In file included from test.c:1:
/usr/include/sys/ipc.h:54: syntax error before `ushort'
In file included from test.c:1:
/usr/include/sys/ipc.h:95: syntax error before `ftok'
/usr/include/sys/ipc.h:95: warning: data definition has no type or storage class
In file included from test.c:2:
/usr/include/sys/shm.h:57: syntax error before `pid_t'
/usr/include/sys/shm.h:60: syntax error before `time_t'
/usr/include/sys/shm.h:93: syntax error before `int'

The fix is trivial, and comes from FreeBSD ports.  Just include sys/types.h
before those two other includes.