libiberty: Fix psignal parameter type

libiberty/strsignal.c

 /* Extended support for using signal values.
    Written by Fred Fish.  fnf@cygnus.com
    This file is in the public domain.  */
 
 #include "config.h"
 #include "ansidecl.h"
 #include "libiberty.h"
 
 /* We need to declare sys_siglist, because even if the system provides
    it we can't assume that it is declared in <signal.h> (for example,
@@ skipping 520 matching lines @@
         {
           signo = 0;
         }
     }
   return (signo);
 }
 
 
 /*
 
-@deftypefn Supplemental void psignal (int @var{signo}, char *@var{message})
+@deftypefn Supplemental void psignal (int @var{signo}, const char *@var{message})
 
 Print @var{message} to the standard error, followed by a colon,
 followed by the description of the signal specified by @var{signo},
 followed by a newline.
 
 @end deftypefn
 
 */
 
 #ifndef HAVE_PSIGNAL
 
 void
-psignal (int signo, char *message)
+psignal (int signo, const char *message)
 {
   if (signal_names == NULL)
     {
       init_signal_tables ();
     }
   if ((signo <= 0) || (signo >= sys_nsig))
     {
       fprintf (stderr, "%s: unknown signal\n", message);
     }
   else
@@ skipping 36 matching lines @@
       name = (name == NULL) ? "<NULL>" : name;
       msg = strsignal (signo);
       msg = (msg == NULL) ? "<NULL>" : msg;
       printf ("%-4d%-18s%s\n", signo, name, msg);
     }
 
   return 0;
 }
 
 #endif