add missing Makefile.am in include/osmocore/protocol directory
diff --git a/include/osmocore/protocol/Makefile.am b/include/osmocore/protocol/Makefile.am
new file mode 100644
index 0000000..6d8883e
--- /dev/null
+++ b/include/osmocore/protocol/Makefile.am
@@ -0,0 +1,3 @@
+osmocore_proto_HEADERS = gsm_04_08.h gsm_04_11.h gsm_04_80.h gsm_08_58.h gsm_12_21.h
+
+osmocore_protodir = $(includedir)/osmocore/protocol