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

include/lib.h

@@ -36,16 +36,6 @@ void _loadname(const char *_name, message *_msgptr);
 int _len(const char *_s);
 void _begsig(int _dummy);
 
-int getprocnr(void);
-int getnprocnr(pid_t pid);
-int getpprocnr(void);
-int _pm_findproc(char *proc_name, int *proc_nr);
-int mapdriver(char *label, int major);
-pid_t getnpid(endpoint_t proc_ep);
-uid_t getnuid(endpoint_t proc_ep);
-gid_t getngid(endpoint_t proc_ep);
-int checkperms(endpoint_t endpt, char *path, size_t size);
-int copyfd(endpoint_t endpt, int fd, int what);
 ssize_t pread64(int fd, void *buf, size_t count, u64_t where);
 ssize_t pwrite64(int fd, const void *buf, size_t count, u64_t where);