Terminal multiplexer

The new terminal_mux server is able to provide multiple terminal
sessions over one terminal-client session. The user can switch
between the different sessions using the keyboard shortcut C-y,
which brings up an ncurses-based menu.
foc: Use git for contrib preparation

Download Fiasco.OC/L4RE from our 'GitHub' fork. Deleted all patches.
foc: SVN revision r42
foc_arndale: Added 'create_buildir' support
base-foc: Generate u-boot image if 'uboot' SPEC is set
Arndale: Build uImage, kernel, bootstrap
foc: Change core's base address
foc: Arndale kernel configuration
foc: Use L2-cache synchronization calls

Replace L1 cache clean operations with L2 versions.
foc: Make context area configurable in core

Make 'context_area_virtual_base' platform configurable. On Arndale, we
need to move the context area to a location that does not interfere with
the address range of physical memory.
foc: Add 'uboot' spec to Arndale
usb: Arndale EHCI controller support
foc: SVN revision r47
usb: Move driver into library

This raised the opportunity to structure the library more cleanly for each
supported platform.
Fixed some unused parameters warnings

They cause problems when using -Werror in your compilation.
base-linux: Don't busywait if lx_pollpid returns 0

This happened when I killed one of the genode clients which was
tracked via an expception_handler. In this case the wait4 syscall
returned 0 and the for(;;) was looped eternally. This caused an
100% CPU utilization for the core binary.
Add the 'cxx' lib in base.mk for 64-bit Linux

This is a follow-up fix for fae63f4fa9df237a5fa3d658b870def17e82f265.
Thanks to Christian Prochaska for the patch.
timer: Don't set default cap as custom cap

Without the patch the signal cap was ever transferred to the timer session
when a usleep/msleep was called, even when unneeded. On base-nova this
causes the allocation of new capability indexes which are not freed up.
So the timer service run quickly out of indexes and get out of order...

Related to issue #1
Remove context area from physical RAM allocator

In base-fiasco, base-foc and base-pistachio, physical memory gets mapped
1:1 to core virtual memory. When the 'Ram_session_component' allocates
physical memory for a client, it zeroes out the corresponding area in
core's virtual address space and then maps the area to the client. If this
area overlaps with core's virtual thread context area (usually at
0x40000000-0x4fffffff), the stack of one or more core threads can get
overwritten.

To avoid this problem, with this patch, the thread context area gets
removed from the physical RAM allocator on these platforms.

Fixes #660.
nova: add syscall pt_ctrl bindings

Issue #667