Make the package autoreconfigurable

Signed-off-by: Denis Bodor <lefinnois@lefinnois.net>
[Gustavo: update for 0.8.8]

diff -Nura libstrophe-0.8.8.orig/m4/.empty libstrophe-0.8.8/m4/.empty
--- libstrophe-0.8.8.orig/m4/.empty	1969-12-31 21:00:00.000000000 -0300
+++ libstrophe-0.8.8/m4/.empty	2015-09-23 19:29:37.893688227 -0300
@@ -0,0 +1,2 @@
+
+
diff -Nura libstrophe-0.8.8.orig/Makefile.am libstrophe-0.8.8/Makefile.am
--- libstrophe-0.8.8.orig/Makefile.am	2015-09-23 19:26:10.960492781 -0300
+++ libstrophe-0.8.8/Makefile.am	2015-09-23 19:29:17.265970964 -0300
@@ -1,4 +1,4 @@
-AUTOMAKE_OPTIONS = subdir-objects
+AUTOMAKE_OPTIONS = subdir-objects foreign
 
 ACLOCAL_AMFLAGS = -I m4
 AM_CFLAGS = -g -Wall