emu: Create an app that allows to communicate with a SGSN

This code can open a BSSGP connection toward a SGSN and will
inititate the unblocking. It does not send any user data.
diff --git a/.gitignore b/.gitignore
index fec1b98..07fde56 100644
--- a/.gitignore
+++ b/.gitignore
@@ -29,9 +29,10 @@
 src/osmo-pcu-remote
 
 # tests
+.dirstamp
 tests/atconfig
 tests/package.m4
-tests/rlcmac/.dirstamp
 tests/rlcmac/RLCMACTest
+tests/emu/pcu_emu
 tests/testsuite
 tests/testsuite.log