Fix cppcheck warnings.

src/funcs.c

@@ -2414,7 +2414,7 @@ static int FShell(func_info *info)
 
     /* Redirect stdin to /dev/null */
     int stdin_dup;
-    int devnull = -1;
+    int devnull;
 
     DBufInit(&buf);
     if (RunDisabled) return E_RUN_DISABLED;

src/utils.c

@@ -37,7 +37,7 @@ static char const DontEscapeMe[] =
 int system1(char const *cmd)
 {
     int stdin_dup = dup(STDIN_FILENO);
-    int devnull = -1;
+    int devnull;
     int r;
 
     if (stdin_dup >= 0) {