SMPP: Implement SMPP Osmocom Estensions on MO-SMS

An ESME can now be configured in the VTY to enable osmocom-extensions,
which will add vendor-specific SMPP TLVs for RxLev/RxQual/ARFCN/IMEI and
transmit power to the SMPP DELIVER-SM message type.
diff --git a/openbsc/configure.ac b/openbsc/configure.ac
index 7004f96..cdefcaf 100644
--- a/openbsc/configure.ac
+++ b/openbsc/configure.ac
@@ -21,7 +21,7 @@
 
 PKG_CHECK_MODULES(LIBOSMOCORE, libosmocore >= 0.5.3.60)
 PKG_CHECK_MODULES(LIBOSMOVTY, libosmovty >= 0.3.0)
-PKG_CHECK_MODULES(LIBOSMOGSM, libosmogsm >= 0.3.0)
+PKG_CHECK_MODULES(LIBOSMOGSM, libosmogsm >= 0.6.0)
 PKG_CHECK_MODULES(LIBOSMOABIS, libosmoabis >= 0.1.0)
 PKG_CHECK_MODULES(LIBOSMOGB, libosmogb >= 0.5.2)