Update autoconf prologue to use "foreign" strictness.

Upstream-Status: Pending
Signed-off-by: Ross Burton <ross.burton@intel.com>

diff --git a/configure.ac b/configure.ac
index d974461..a20dfa8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,2 +2,3 @@ dnl Process this file with autoconf to produce a configure script.
-AC_INIT(which.c)
-AM_INIT_AUTOMAKE(which, 2.20)
+AC_INIT([which],[2.20])
+AC_CONFIG_SRCDIR(which.c)
+AM_INIT_AUTOMAKE([foreign])