Return zero when reporting our version.

When called with -V to ask for our version, return 0 rather than 1.
This is the usual behaviour observed by ssh(1) and other Unix commands.
Also use exit() rather than cleanup_exit() in pscp.c and psftp.c ; at
this point we have nothing to cleanup!

pscp.c

@@ -2272,7 +2272,7 @@ void version(void)
     char *buildinfo_text = buildinfo("\n");
     printf("pscp: %s\n%s\n", ver, buildinfo_text);
     sfree(buildinfo_text);
-    cleanup_exit(1);
+    exit(0);
 }
 
 void cmdline_error(const char *p, ...)

psftp.c

@@ -2670,7 +2670,7 @@ static void version(void)
   char *buildinfo_text = buildinfo("\n");
   printf("psftp: %s\n%s\n", ver, buildinfo_text);
   sfree(buildinfo_text);
-  cleanup_exit(1);
+  exit(0);
 }
 
 /*

unix/uxpgnt.c

@@ -145,7 +145,7 @@ static void version(void)
     char *buildinfo_text = buildinfo("\n");
     printf("pageant: %s\n%s\n", ver, buildinfo_text);
     sfree(buildinfo_text);
-    exit(1);
+    exit(0);
 }
 
 void keylist_update(void)

unix/uxplink.c

@@ -599,7 +599,7 @@ static void version(void)
     char *buildinfo_text = buildinfo("\n");
     printf("plink: %s\n%s\n", ver, buildinfo_text);
     sfree(buildinfo_text);
-    exit(1);
+    exit(0);
 }
 
 void frontend_net_error_pending(void) {}

windows/winplink.c

@@ -228,7 +228,7 @@ static void version(void)
     char *buildinfo_text = buildinfo("\n");
     printf("plink: %s\n%s\n", ver, buildinfo_text);
     sfree(buildinfo_text);
-    exit(1);
+    exit(0);
 }
 
 char *do_select(SOCKET skt, int startup)