Check md5 sum of initramfs file in l4lx run-script

* Always download md5sum file and check downloaded binaries
* Extend sleep time in l4linux_netperf script, so that DHCP has enough time
* Fix regexp rule in l4linux_netperf run script to work with MAC addresses
  containing only numbers

Fix #787
doc: Update location of VESA driver
nic_bridge: Documentation update
Don't use daemonized telnet in netcat run-script

Fix #782
base: add method to withdraw memory w/o allocating

The given number of bytes is consumed but not actually allocated. This
feature may be used for accounting and use memory within core which is
in fact provided by a session client.

Fixes #792.
noux: add local cpu and ram service

Use a local CPU service to prevent a redirection to noux' parent (in
this case init which does not know noux' local capabilities).

Fixes #791.
linux: thread name wrongly truncated by one byte

The terminating NUL char was not considerd in the calculation of
the space needed for storing the string.

Fixes #790.
core: use label for init's Cpu_session

Fixes #789.
core: add session args filter to Core_child

Add the filter_session_args() method to Core_child to prefix the labels
of its children.

Fixes #789.
core: remove hardcoded 'init' from Log output

Until now the print procedure call in the Log_session_component
did contain a hardcoded 'init' string. Adding a method to filter
the session args to prefix the label and labelling the initial
Cpu_connection for the init-process enabled us to remove the
hardcoded string.

Fixes #789.
hw: initialize Platform_thread::_main_thread right

Ref #766
hw & arm: use sp to hand out main UTCB pointer

Also don't hand out UTCB pointers to cores main thread and to threads
other than main threads.

Ref #766
hw: use generic crt0.s for progs other than core

Use '__initial_sp' instead of '_main_utcb' to receive a main threads
UTCB pointer outside core.

Ref #766
base: provide BSS boundary marks in genode.ld

This enables us to use the generic linker script for
base-hw also.

Ref #766
hw: use generic genode.ld

Ref #766
crt0 cleanup

- use the generic 'crt0.s' for Linux
- move the read-only '__dso_handle' definition into the '.text' section
- move the '__initial_sp' definition into the '.bss' section
- remove the '_main_utcb' definition

Part of #766.
nic_bridge: increase entrypoint stack size

Issue #782
Let Git ignore libports/include/x86emu

The headers are mere symlinks created via 'make prepare'.