non recursive string_replace

Previous to this commit a replacement that also contains the needle
would cause an endless loop

utils.c

@@ -43,12 +43,8 @@ char *string_replace(const char *needle, const char *replacement,
         sprintf(tmp + strlen(tmp), "%s%s", replacement, start + strlen(needle));
         free(haystack);
 
-        if (strstr(tmp, needle)) {
-                return string_replace(needle, replacement, tmp);
-        } else {
         return tmp;
 }
-}
 
 int digit_count(int i)
 {