Add NBSD-like Minix system includes.

nbsd_include/sys/sysctl.h

@@ -0,0 +1,22 @@
+#ifndef _SYS_SYSCTL_H
+#define _SYS_SYSCTL_H
+
+/*
+ * sysctl() is not supported. Warn non-libc programs including this header.
+ */
+#ifndef _LIBC
+#warning Including sysctl.h header. sysctl() is not supported in Minix.
+#endif /* !_LIBC */
+
+/*
+ * Used by gmon.
+ */
+struct clockinfo {
+	int	hz;		/* clock frequency */
+	int	tick;		/* micro-seconds per hz tick */
+	int	tickadj;	/* clock skew rate for adjtime() */
+	int	stathz;		/* statistics clock frequency */
+	int	profhz;		/* profiling clock frequency */
+};
+
+#endif /* _SYS_SYSCTL_H */