misc: just eliminate several 'unused' warning messages

[ plus we also play catch up on some earlier changes ]
[ that impacted skill.c, after using --enable-skill! ]

Signed-off-by: Jim Warner <james.warner@comcast.net>

ps/output.c

@@ -1216,8 +1216,10 @@ setREL1(LXCNAME)
 static int pr_context(char *restrict const outbuf, const proc_t *restrict const pp){
   static void (*ps_freecon)(char*) = 0;
   static int (*ps_getpidcon)(pid_t pid, char **context) = 0;
+#if ENABLE_LIBSELINUX
   static int (*ps_is_selinux_enabled)(void) = 0;
   static int tried_load = 0;
+#endif
   static int selinux_enabled = 0;
   size_t len;
   char *context;

ps/sortformat.c

@@ -236,7 +236,7 @@ static const char *format_parse(sf_node *sfn){
       need_item=0;
     }
   } while (*++walk);
-out:
+
   if(!items){
     free(buf);
     goto empty;

ps/stacktrace.c

@@ -172,6 +172,7 @@ void debug(int method, char *prog_name){
   while(x);  /* wait for debugger? */
 }
 
+#ifdef DEBUG
 /************/
 static void stack_trace_sigsegv(int signum){
   (void)signum;
@@ -179,7 +180,6 @@ static void stack_trace_sigsegv(int signum){
 }
 
 /************/
-#ifdef DEBUG
 void init_stack_trace(char *prog_name){
   stored_prog_name = prog_name;
   signal(SIGSEGV, stack_trace_sigsegv);