ldso: add __L4_ThreadSwitch to ldso symbol.map

This wasn't necessary before because we built an l4 library for
Pistachio and linked it against each application. With the new linker,
we compile the required files from within Genode and create a syscall
library that is only linked to ldso. If a program uses system calls
directly, for example, DDE kit's spinlock implementation, the required
symbols must be made globally accessible.

Fixes #1306
Fix compiler warning about uninitialized variable

Fixes #1051
libc: support F_SETFD && FD_CLOEXEC ioctl

Issue #1308
vbox: support routing serial output to Genode

Fixes #1308
run: relax IP power plug recognition + serial EOF

* To communicate with IP power plug devices from Koukaam, to remote
  control power supply of test boards, don't parse minor versions, but
  support different IP power plugs
* TCL's expect may report an EOF when reading from the spawned serial
  terminal, especially when using 'socat' to stream serial over TCP/IP,
  although the spawned child is still running and delivering content.
  This problem is clearly not dependent on the characters send, but
  possibly due to strange pipe signals. When piping the serial output
  through 'tr' the problem vanishs.
foc: relax parsing of boot process termination

Until now, the successful termination of the boot process was recognized
when 'expect' saw the first L4 bootstrapper output on serial line. On sytems
with initially shaky serial connection like Versatile Express, where the serial
line baudrate changes with the bootstrapper initialization, the first expected
line might be missing. Therefore, change the expected line to the first
Fiasco.OC kernel output.
qt5: let QNitpickerViewWidget react to focus event

With this patch, when calling 'setFocus()' on a QNitpickerViewWidget, the
Nitpicker view gets the input focus (provided that the parent Qt window
already had it).

Fixes #1314
qt5: fix include dir of 'qt5_qpa_nitpicker' library

Fixes #1315
qt5: set explicit routes for Nitpicker's 'Framebuffer' and 'Input' sessions

Setting explicit routes for Nitpicker's 'Framebuffer' and 'Input' sessionsi
avoids ambiguities if a Qt application provides these services, too.

Fixes #1316