libsys: various updates

- move system calls for use by services from libminlib into libsys;
- move srv_fork(2) and srv_kill(2) from RS and into libsys;
- replace getprocnr(2) with sef_self(3);
- rename previous getnprocnr(2) to getprocnr(2);
- clean up getepinfo(2);
- change all libsys calls that used _syscall to use _taskcall, so as
  to avoid going through errno to pass errors; this is already how
  most calls work anyway, and many of the calls previously using
  _syscall were already assumed to return the actual error;
- initialize request messages to zero, for future compatibility
  (note that this does not include PCI calls, which are in need of a
  much bigger overhaul, nor kernel calls);
- clean up more of dead DS code as a side effect.

Change-Id: I8788f54c68598fcf58e23486e270c2d749780ebb

lib/libsys/vm_query_exit.c

@@ -0,0 +1,37 @@
+#include "syslib.h"
+#include <unistd.h>
+#include <string.h>
+
+/*
+ * Return a negative error code if the query itself or the processing of the
+ * query resulted in an error.
+ * Return 1 if there are more processes waiting to be queried.
+ * Return 0 if there are no more processes.
+ * Note that for the return value of 0 and 1, the 'endpt' is set accordingly.
+ */
+int
+vm_query_exit(int *endpt)
+{
+	message m;
+	int r;
+
+	memset(&m, 0, sizeof(m));
+	r = _taskcall(VM_PROC_NR, VM_QUERY_EXIT, &m);
+	if (r != OK)
+		return r;
+	if (endpt == NULL)
+		return EFAULT;
+
+	*endpt = m.VM_QUERY_RET_PT;
+	return (m.VM_QUERY_IS_MORE ? 1 : 0);
+}
+
+int
+vm_watch_exit(endpoint_t ep)
+{
+	message m;
+
+	memset(&m, 0, sizeof(m));
+	m.VM_WE_EP = ep;
+	return _taskcall(VM_PROC_NR, VM_WATCH_EXIT, &m);
+}