Require newer libosmocore to avoid compile failures

Older commit started using OSMO_IMSI_BUF_SIZE, only available in
libosmocore 1.1.0 onwards, but forgot to increase the values in
configure.ac.

Fixes: 2c076bcb4dc1bc2ada340441c2f898c55318209f
Change-Id: Iaf5f276a092c695a5f077551d9784652c2289424
diff --git a/debian/control b/debian/control
index 9ff9d88..497788c 100644
--- a/debian/control
+++ b/debian/control
@@ -7,7 +7,7 @@
                dh-systemd (>= 1.5),
                autotools-dev,
                pkg-config,
-               libosmocore-dev (>= 0.10.1),
+               libosmocore-dev (>= 1.1.0),
                osmo-gsm-manuals-dev
 Standards-Version: 3.9.8
 Homepage: http://osmocom.org/projects/osmopcu