core: add session label member

This member is used to save the actual session label for further use
within core.
base: add attach_exec short-cut to Rm_session XXX

There alread is a short-cut for attaching a dataspace executable but
this method (attach_executable()) needs a local address.

*** use a more fitting method name ***
noux: short-cut for read(..., 0)

If the bytes left to read are 0 we drop out early w/o involving the
packet-stream.
noux: increase the stack size of rpc-ep thread

The current limit (4/8 KiB) is too small when tracing will be enabled.
base: add name() to struct rpc_name

This method maybe used to get the actual name of the
corresponding RPC-function.
base: add serialized rdtsc function

Use cpuid instruction to prevent the cpu from reordering the rdtsc
instruction when obtaining the TSC value.

Though it is questionable if "mfence; rdtsc" or "rdtscp" would be
a better choice.
base: add Trace_session header
base: add basic Trace header

This includes the Trace_buffer declaration and definition of most common
functions used to access the buffer and policy.
core: add Trace_session_component
base: add trace accessors to Thread_base interface
base: add tb_dataspace() to Cpu_session interface
base: add tb_dataspace() to Expanding_c_s_c
core: add TRACE
base: add trace startup-code to _main()
linux: add Trace_session_component
linux: initial Tracebuffer support
Add trace + trace_session tests
base: add rpc/signal tracepoints
os: initial Trace_fs server
ports: add noux trace_fs run-script