While importing trace sources as trace subjects into a TRACE session,
the session quota might become depleted. The TRACE session already keeps
track of the session quota via an allocator guard but the 'subjects' RPC
function missed to handle the out-of-memory condition. This patch
reflects the error condition as an 'Out_of_metadata' exception to the
TRACE client. It also contains an extension of the trace test to
exercise the corner case.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
