Fiasco.OC: introduce Cap_index (fixes #149, #112)

This commit introduces a Cap_index class for Fiasco.OC's capabilities.
A Cap_index is a combination of the global capability id, that is used by Genode
to correctly identify a kernel-object, and a corresponding entry in a
protection-domain's (kernel-)capability-space. The cap-indices are non-copyable,
unique objects, that are held in a Cap_map. The Cap_map is used to re-find
capabilities already present in the protection-domain, when a capability is
received via IPC. The retrieval of capabilities effectively fixes issue #112,
meaning the waste of capability-space entries.
Because Cap_index objects are non-copyable (their address indicates the position
in the capability-space of the pd), they are inappropriate to use as
Native_capability. Therefore, Native_capability is implemented as a reference
to Cap_index objects. This design seems to be a good pre-condition to implement
smart-pointers for entries in the capability-space, and thereby closing existing
leaks (please refer to issue #32).

Cap_index, Cap_map, and the allocator for Cap_index objects are designed in a way,
that it should be relatively easy to apply the same concept to NOVA also. By now,
these classes are located in the `base-foc` repository, but they intentionally
contain no Fiasco.OC specific elements.

The previously explained changes had extensive impact on the whole Fiasco.OC
platform implementation, due to various dependencies. The following things had to
be changed:

* The Thread object's startup and destruction routine is re-arranged, to
  enable another thread (that calls the Thread destructor) gaining the
  capability id of the thread's gate to remove it from the Cap_map, the
  thread's UTCB had to be made available to the caller, because there
  is the current location of that id. After having the UTCB available
  in the Thread object for that reason, the whole thread bootstrapping
  could be simplified.
* In the course of changing the Native_capability's semantic, a new Cap_mapping
  class was introduced in core, that facilitates the establishment and
  destruction of capability mappings between core and it's client's, especially
  mappings related to Platform_thread and Platform_task, that are relevant to
  task and thread creation and destruction. Thereby, the destruction of
  threads had to be reworked, which effectively removed a bug (issue #149)
  where some threads weren't destroyed properly.
* In the quick fix for issue #112, something similar to the Cap_map was
  introduced available in all processes. Moreover, some kind of a capability
  map already existed in core, to handle cap-session request properly. The
  introduction of the Cap_map unified both structures, so that the
  cap-session component code in core had to be reworked too.
* The platform initialization code had to be changed sligthly due to the
  changes in Native_capability
* The vcpu initialization in the L4Linux support library had to be adapted
  according to the already mentioned changes in the Thread object's bootstrap
  code.
Fix compare_output_to in run tool (fix #162)

In the compare_output_to function in the run tool a check was introduced,
whether the given arguments are empty, and if so if the output string is it
too. Without this patch compare_output_to succeeded when the given pattern
was empty but output wasn't. Please refer to issue #162.
Fiasco.OC: remove cap_alloc library (fix #160)

The cap_alloc library became redundant and doesn't compile any longer.
This commit simply removes it. Please, refer to issue #160.
Let cap_integrity test be more expressive

By using the `compare_output_to` method from the run tool instead of using
regexp in the cap_integrity run-script, the test outputs the undesired lines
instead of just signaling that the test failed.
Rewrite cap_integrity test for Fiasco.OC (fix #161)

By commit d287b9d89387d8d307c11594413d7ab47429827f the Native_capability
class changed fundamentally in the Fiasco.OC platform code of Genode. Thereby
the cap_integrity test got incompatible with it. This commit introduces a
separate test implementation for Fiasco.OC that does semantically the same
like the old test. Please refer to issue #161.
Add VIM to 'noux_bash.run'
Let Noux deliver EOF when pressing control-d
Ignore suspicious wake-up messages on OKL4