Use setenv(), fix warnings

- Fix -Wundef -Wold-style-definition warnings
  - Make pll_free() static

[jc: original patch by Timo had another unrelated bits:

  - Use setenv() instead of putenv()

 I'm postponing that part for now.]

Signed-off-by: Timo Hirvonen <tihirvon@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

fetch-pack.c

@@ -82,7 +82,7 @@ static void mark_common(struct commit *commit,
   Get the next rev to send, ignoring the common.
 */
 
-static const unsigned char* get_rev()
+static const unsigned char* get_rev(void)
 {
 	struct commit *commit = NULL;