avoid gcc warnings like:

ps/output.c:341:6: warning: the address of ‘forest_prefix’ will always evaluate as ‘true’

--- a/ps/output.c
+++ b/ps/output.c
@@ -338,7 +338,7 @@ static int pr_args(char *restrict const 
   unsigned flags;
   int rightward=max_rightward;
 
-  if(forest_prefix){
+  if(/*forest_prefix*/1){
     int fh = forest_helper(outbuf);
     endp += fh;
     rightward -= fh;
@@ -405,7 +405,7 @@ static int pr_cgroup(char *restrict cons
  if(pp->cgroup && *pp->cgroup) {
    char *endp = outbuf;
    int rightward=max_rightward;
-   if(forest_prefix){
+   if(/*forest_prefix*/1){
        int fh = forest_helper(outbuf);
        endp += fh;
        rightward -= fh;
@@ -365,7 +365,7 @@ static int pr_comm(char *restrict const 
   unsigned flags;
   int rightward=max_rightward;
   
-  if(forest_prefix){
+  if(/*forest_prefix*/1){
     int fh = forest_helper(outbuf);
     endp += fh;
     rightward -= fh;
@@ -390,7 +390,7 @@ static int pr_fname(char *restrict const
   char *endp = outbuf;
   int rightward = max_rightward;
   
-  if(forest_prefix){
+  if(/*forest_prefix*/1){
     int fh = forest_helper(outbuf);
     endp += fh;
     rightward -= fh;