apps/examples/ostest: Add a test for the sigprocmask, sighold, and sigrelse

arch/sim/src/nuttx-names.dat

@@ -33,6 +33,9 @@ rmdir          NXrmdir
 seekdir        NXseekdir
 select         NXselect
 send           NXsend
+sighold        NXsighold
+sigprocmask    NXsigprocmask
+sigrelse       NXsigrelse
 sendto         NXsendto
 sleep          NXsleep
 socket         NXsocket

libc/signal/sig_relse.c

@@ -52,7 +52,7 @@
  *
  ****************************************************************************/
 
-int sighold(int signo)
+int sigrelse(int signo)
 {
   sigset_t set;
   int ret;