app: Introduce some routines to help with application startup

The plan is to collect structs and routines for application
setup and remove many copies of the boilerplate code we have
right now. This starts with routines to ignore certain signals
and the stderr init code.

Increment the age of the library because a new interface was added.
diff --git a/include/osmocom/core/Makefile.am b/include/osmocom/core/Makefile.am
index b21e047..3698873 100644
--- a/include/osmocom/core/Makefile.am
+++ b/include/osmocom/core/Makefile.am
@@ -3,7 +3,7 @@
 		   gsmtap.h write_queue.h \
 		   logging.h rate_ctr.h gsmtap_util.h \
 		   plugin.h crc16.h panic.h process.h msgfile.h \
-		   backtrace.h conv.h
+		   backtrace.h conv.h application.h
 
 if ENABLE_TALLOC
 osmocore_HEADERS += talloc.h