Linux: use 'SYS_wait4' instead of 'SYS_waitpid'

'SYS_waitpid' does not exist on x86_64 Linux, but 'SYS_wait4' does.

Fixes #615.
Let memcmp correspond to the C standard (fix #628)

By now, the memcmp implementation of Genode's basic string utilities just
returned whether two memory blocks are equal or differ. It gave no hint which
block is greater, or lesser than the other one. This isn't the behaviour
anticipated by implementations that rely on the C standard memcmp, e.g. GCC's
libsupc++, or the nic_bridge's AVL tree implementation.
Remove timer from hello run script (fix #629)

Currently, the hello run script of the hello_tutorial misses some services the
timer driver needs on various platforms. The hello_tutorial is meant for
educational purposes only. So it's desireable to keep it simple. Instead of
complexifying the configuration, this commit just removes the timer from the
example.
Fix OMAP4 uart driver compilation

Fixes #630
base: fix wrap around bug in avl allocator

Fix #631
nova: use lock guard instead of explicit calls

If an exception is thrown the lock is released automatically, so that
other callers may get a capability index if in between some are freed. Fixes
some deadlocks if Genode is short on capability indexes.

Related to #625
nova: ease debugging if no cap indexes are left

If we ran out of capabilities indexes, the bit allocator throws an exception.
If this happens the code seems to hang and nothing happens.

Instead one could catch the exception and print some diagnostic message.
This would be nice, but don't work. Printing some diagnostic message itself
tries to do potentially IPC and will allocate new capability indexes at
least for the receive window.

So, catch the exception and let the thread die, so at least the instruction
pointer is left as trace to identify the reason of the trouble.

Fixes #625
Adapt qt4 to Input::Event changes

We need to make the event checks more explicit because 'code' is not
exclusively used for key event anymore.
tar_rom: let unkown file throw Root::Invalid_args
Coding style fixes
libc_lwip_nic_dhcp: Add static IP configuration
nic_bridge: Add static IP address configuration
nic_bridge: Add tests for static IP address configuration