GSUP routing was introduced when adding the E interface. Hence that was the
first realm where routing errors could occur. I did notice back then that this
message type was special: it does not convey a response to a particular message
kind -- it does not make sense, for example, to return an Updating Location
Error cause, and do that for all conceivable message types. Instead, this tells
the sender that a deeper error exists, i.e. that the desired peer is completely
gone and unreachable.
I did not foresee though that for D-GSM, there would also be arbitrary GSUP
proxy routing, and that this error is not limited to E interface semantics.
From today's point of view, adding the "_E_" in the name was a mistake.
Remove that "_E_" to yield OSMO_GSUP_MSGT_ROUTING_ERROR (with unchanged message
type discriminator), but provide a #define linking the old name
OSMO_GSUP_MSGT_E_ROUTING_ERROR to the new one.
The only visible change should be that osmo_gsup_message_type_names[] now
returns the new name without "_E_". I am not aware of any regression test
fallout from that.
Change-Id: Ic8e8bd11522d6c51ac7aaf946516cbce26bc6e1e