Add prototypes for the userland gmon support functions, which normally

live in src/lib/libc/gmon/gmon.c. glibc puts these prototypes in the same
header, so put them here for the sake of consistency.

PR:		bin/4459
Reviewed by:	bde

sys/sys/gmon.h

@@ -228,6 +228,15 @@ void	mexitcount(uintfptr_t selfpc);
 void	nullfunc(void);
 void	nullfunc_loop(void);
 
+#else /* !_KERNEL */
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+void	moncontrol(int);
+void	monstartup(u_long, u_long);
+__END_DECLS
+
 #endif /* _KERNEL */
 
 #endif /* !_SYS_GMON_H_ */