steps towards making 'make distcheck' work

'make distcheck' checks for out-of-source-tree builds and whether
the distribution tarball includes all source files.  This commit
fixes many problems, except some remaining with src/test still
to-be-fixd.
diff --git a/src/hnbap/Makefile.am b/src/hnbap/Makefile.am
index e152587..0362871 100644
--- a/src/hnbap/Makefile.am
+++ b/src/hnbap/Makefile.am
@@ -236,7 +236,7 @@
 
 noinst_LIBRARIES=libosmo-asn1-hnbap.a
 libosmo_asn1_hnbap_a_SOURCES=$(ASN_MODULE_SOURCES)
-include_HEADERS = $(ASN_MODULE_INC)
+noinst_HEADERS = $(ASN_MODULE_INC)
 libosmo_asn1_hnbap_a_LIBADD=$(ASN1C_LDADD)
 
 regen: regenerate-from-asn1-source