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
---
M configure.ac
M include/osmocom/Makefile.am
M include/osmocom/msc/Makefile.am
D include/osmocom/msc/smpp.h
A include/osmocom/smpp/Makefile.am
A include/osmocom/smpp/smpp.h
R include/osmocom/smpp/smpp_smsc.h
M src/Makefile.am
M src/libmsc/Makefile.am
M src/libmsc/gsm_04_11.c
A src/libsmpputil/Makefile.am
R src/libsmpputil/smpp_msc.c
R src/libsmpputil/smpp_smsc.c
R src/libsmpputil/smpp_utils.c
R src/libsmpputil/smpp_vty.c
M src/osmo-msc/Makefile.am
M src/osmo-msc/msc_main.c
M src/utils/Makefile.am
M src/utils/smpp_mirror.c
M tests/db_sms/Makefile.am
M tests/msc_vlr/Makefile.am
M tests/smpp/Makefile.am
M tests/smpp/smpp_test.c
M tests/sms_queue/Makefile.am
M tests/stubs.c
25 files changed, 113 insertions(+), 100 deletions(-)