Remove remote shell support from libc

The remote shell facilities are past deprecation and there is an
obligation to prevent their use rather than to support them. This patch
removes the related function definitions from 'unistd.h', which have not
been been included in the Genode libc ABI regardless.

Fix #2530

repos/libports/lib/mk/libc-net.mk

@@ -21,8 +21,6 @@ SRC_C += vars.c
 # b64_ntop
 SRC_C += base64.c
 
-SRC_C += rcmd.c rcmdsh.c
-
 include $(REP_DIR)/lib/mk/libc-common.inc
 
 INC_DIR += $(REP_DIR)/include/libc

repos/libports/ports/libc.hash

@@ -1 +1 @@
-5871e71bb99dab10faab21931750c30e8a02d980
+c9c17345f57cb2f827c271806df456d829e32ce3

repos/libports/src/lib/libc/patches/README

@@ -26,3 +26,7 @@ Manual modifications
 :'src/lib/libc/resolv/res_send.c':
 
   Disable usage of kqueue and fix building libresolv when kqueue is disabled.
+
+:'src/lib/libc/include/unistd.h':
+
+  Remove definitions for remote network commands over unencrypted streams.

repos/libports/src/lib/libc/patches/rcmd.patch

@@ -0,0 +1,32 @@
+--- src/lib/libc/include/unistd.h
++++ src/lib/libc/include/unistd.h
+@@ -510,8 +510,6 @@
+ int	 getresuid(uid_t *, uid_t *, uid_t *);
+ char	*getusershell(void);
+ int	 initgroups(const char *, gid_t);
+-int	 iruserok(unsigned long, int, const char *, const char *);
+-int	 iruserok_sa(const void *, int, int, const char *, const char *);
+ int	 issetugid(void);
+ long	 lpathconf(const char *, int);
+ #ifndef _MKDTEMP_DECLARED
+@@ -533,20 +531,12 @@
+ #endif
+ int	 nfssvc(int, void *);
+ int	 profil(char *, size_t, vm_offset_t, int);
+-int	 rcmd(char **, int, const char *, const char *, const char *, int *);
+-int	 rcmd_af(char **, int, const char *,
+-		const char *, const char *, int *, int);
+-int	 rcmdsh(char **, int, const char *,
+-		const char *, const char *, const char *);
+ char	*re_comp(const char *);
+ int	 re_exec(const char *);
+ int	 reboot(int);
+ int	 revoke(const char *);
+ pid_t	 rfork(int);
+ pid_t	 rfork_thread(int, void *, int (*)(void *), void *);
+-int	 rresvport(int *);
+-int	 rresvport_af(int *, int);
+-int	 ruserok(const char *, int, const char *, const char *);
+ #if __BSD_VISIBLE
+ #ifndef _SELECT_DECLARED
+ #define	_SELECT_DECLARED