Fiasco.OC: several capability ref-counter fixes.

This commit fixes several issues that were triggered e.g. by the
'noux_tool_chain' run-script (fix #208 in part). The following problems
are tackled:
* Don't reference count capability selectors within a task that are actually
  controlled by core (all beneath 0x200000), because it's undecideable which
  "version" of a capability selector we currently use, e.g. a thread gets
  destroyed and a new one gets created immediately some other thread might
  have a Native_capability pointing to the already destroyed thread's gate
  capability-slot, that is now a new valid one (the one of the new thread)
* In core we cannot invalidate and remove a capability from the so called
  Cap_map before each reference to it is destroyed, so don't do this in
  Cap_session_component::free, but only reference-decrement within there,
  the actual removal can only be done in Cap_map::remove. Because core also
  has to invalidate a capability to be removed in all protection-domains
  we have to implement a core specific Cap_map::remove method
* When a capability gets inserted into the Cap_map, and we detect an old
  invalid entry with the dame id in the tree, don't just overmap that
  invalid entry (as there exist remaining references to it), but just remove
  it from the tree and allocate an new entry.
* Use the Cap_session_component interface to free a Pager_object when it
  gets dissolved, as its also used for allocation
Fiasco.OC: fix capability ref-counter issue in core

The Cap_mapping abstraction in core shouldn't use a Cap_index directly, but
use Native_capability instead, as it can break reference-counting, as long as
the same Cap_index gets used in a Cap_mapping and a Native_capability. This
commit finally fixes #208.
libc_terminal: add fstat and fake some ioctls, fix #344
libc_terminal: TIOCGETA return always echo on
libports: adjust lwip's TCP_SND_BUF size

The old values were much too small and the current ones are probably to
large but the TCP send throuhgput has increased noticeable (a few MiB/s
on the Pandaboard).

Fixes #343.
Add stdcxx-4.6.1 to libports, fix #339

This patch adds libstdc++ to libports. With the previous version of the
stdcxx library, the build system used the C++ standard library that
comes with the compiler. This mechanism was prone to inconsistencies of
types defined in the header files used at compile time of the tool chain
and the types provided by our libc. By building the C++ standard library
as part of the Genode build process, such inconsistencies cannot happen
anymore.

Note that the patch changes the meaning of the 'stdcxx' library for
users that happened to rely on 'stdcxx' for hybrid Linux/Genode
applications. For such uses, the original mechanism is still available,
in the renamed form of 'toolchain_stdcxx'.
Adapt Qt4 to change of stdcxx, issue #339

The new C++ standard library provided by libports is a shared library.
We need to include it in each run script that uses Qt4.
Extend Cpu_session with thread-affinity API

This patch introduces the functions 'affinity' and 'num_cpus' to the CPU
session interface. The interface extension will allow the assignment of
individual threads to CPUs. At this point, it is just a stub with no
actual platform support.
Fix binary size for 64bit

Every 64-bit binary is effectively 4M too big currently [0]. The GNU linker ld
aligns the text section of the binary to the maximum page size. On i386
the default section alignment is fixed typically to 4K.

Avoid wasting mainly 4M on x86_64 by telling the linker the max page size to
be 4K.

[0] http://sourceware.org/ml/binutils/2009-04/msg00099.html