Introduce libsmpputil

As part of preparation for libosmo-netif migration let's move common SMPP code
into separate build-time library and use it for both smpp_mirror and OsmoMSC
renaming the files if necessary.

While at it we also fix id/password legth limits in smpp_mirror and drop unused
fields from ESME struct.

Related: OS#5568
Change-Id: I61910651bc7c188dc2fb67d96189a66a47e7e8fb
diff --git a/src/Makefile.am b/src/Makefile.am
index 4e7cea1..e23ab10 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -25,8 +25,16 @@
 	libmsc \
 	$(NULL)
 
+if BUILD_SMPP
+
+SUBDIRS += \
+	libsmpputil \
+	utils \
+	$(NULL)
+
+endif
+
 # Programs
 SUBDIRS += \
 	osmo-msc \
-	utils \
 	$(NULL)