bsc/mminfo: Patch timezone and DST in MM Info messages

This adds in-place patching of the time information in the
MM INFORMATION message. The timezone in the 'Local time zone' and
the 'Universal time and local time zone' information elements
and the offset in the 'Network Daylight Saving Time' information
element are optionally set.

The new values are determined by the 'timezone' vty command in the
config_net_bts node. That command is extended by an optional
DST offset parameter.

Tests are provided for the vty part and for the plain
bsc_scan_msc_msg() function.

Sponsored-by: On-Waves ehf
Ticket: OW#978
diff --git a/openbsc/.gitignore b/openbsc/.gitignore
index 79222f7..5955482 100644
--- a/openbsc/.gitignore
+++ b/openbsc/.gitignore
@@ -63,6 +63,7 @@
 tests/abis/abis_test
 tests/si/si_test
 tests/smpp/smpp_test
+tests/bsc/bsc_test
 
 tests/atconfig
 tests/atlocal