Fix make distcheck by adding some header files
diff --git a/include/Makefile.am b/include/Makefile.am
index f5c6487..0de9178 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -1 +1,3 @@
 SUBDIRS = openbsc
+
+noinst_HEADERS = mISDNif.h