x86: increase timeout in qemu's term

Currently `boards/qemu-i386/dist/term.py` expects QEMU to connect in
less than 5 seconds, which is plenty on any user machine. Travis CI,
which we use without paying a cent, sometimes fails to start QEMU in
this is timeframe, though.

This PR increases the timeout to one minute.
make: removed shell_commands dependency
boards/z1: fix cc2420_txrx function in CC2420 driver HAL

When waiting for transmission (to CC2420) to be done,
we were wrongly waiting for UCBUSY bit to be set,
while one should actually wait for that bit to be cleared.
Merge pull request #1382 from Kijewski/qemu-i86-term-timeout

x86: increase timeout in qemu's term
Merge pull request #1386 from haukepetersen/fix_shellcmd_dep

make: removed shell_commands dependency
destiny: deleting packed attribute from socket_internal_t

While testing the tcp implementation on MSBA2 I noticed that
the value of `tcp_input_buffer_end` gets changed whenever acquiring or
releasing the mutex of the struct on the server side.

After deleting the packed attribute of the struct this problem was
resolved and the value stayed the same after acquiring and releasing.

This problem could maybe arise from badly placed cache lines due to
missing padding... I am not sure.

Anyway, I guess using the packed attribute is useless here and makes it
more error-prone.
destiny: Adjust TCP_STACK_SIZE

Currently, the TCP_STACK_SIZE is `KERNEL_CONF_STACKSIZE_DEFAULT`.
However, since printf statements are used in the tcp relevant code,
this stack size is too small (esp. for MSBA2).
Merge pull request #1391 from cgundogan/fix_tcp_kernel_conf_stack_size

destiny: Adjust TCP_STACK_SIZE
Merge pull request #1390 from cgundogan/fix_socket_internal_t_packed_attr

destiny: deleting packed attribute from socket_internal_t
Merge pull request #1388 from rousselk/fix-z1-cc2420-txrx

boards/z1: fix cc2420_txrx function in CC2420 driver HAL