Add the definition _WANT_SEMUN to ensure the definition of the semun structure.

This resolves bug 2991.

Thanks to Nikolaus Klepp for initial patch.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit b7be699a09)

src/kernel/qlock.cpp

@@ -47,6 +47,7 @@
 #include <sys/stat.h>
 #include <sys/file.h>
 #else
+#define _WANT_SEMUN
 #include <sys/sem.h>
 #if defined(__GNU_LIBRARY__) && !defined(_SEM_SEMUN_UNDEFINED) \
     || defined(Q_OS_FREEBSD) || defined(Q_OS_OPENBSD) || defined(Q_OS_NETBSD) || defined(Q_OS_BSDI)