cpu/stm32f1: fix i2c master read for N>2 bytes

This fixes reading more than 2 bytes from the slave device.
In the current implementation the last byte was not read from
data register and the termination sequence buggy.
cpu/stm32f1: fix i2c read for N=2 bytes
core: make sched_runqueue public

Reverting b604832, because thread_yield() needs to access this
information.
core: move thread_yield*() to thread.[ch]

Although it might conceptionally rather belong to the scheduler, the
yield functions are prefixed with thread_ and thus, belong there.
rpl_udp: add non-routing hosts to example
doc: added and fixed some copyright boilerplates
cpu: removed NAKED attribute from ISRs

- removed the __attribute__((naked)) from ISRs
- removed ISR_ENTER() and ISR_EXIT() macros

Rationale: Cortex-Mx MCUs save registers R0-R4 automatically
on calling ISRs. The naked attribute tells the compiler not
to save any other registers. This is fine, as long as the
code in the ISR is not nested. If nested, it will use also
R4 and R5, which will then lead to currupted registers on
exit of the ISR. Removing the naked will fix this.
Copy SEGGER JLink scripts from boards/openmote to boards/cc2538dk.
boards/cc2538dk: Support flashing and debugging using the SEGGER JLink.
sys: fix thread_print_all
drivers: added LPS331AP pressure sensor driver
board/iot-lab_M3: added interface for LPS331AP
tests: added test for LPS331AP sensor driver
Merge pull request #1888 from OlegHahm/license_cleanup

doc: added and fixed some copyright boilerplates
unittests: add test network device

The reasoning behind this commit is twofold:
1. test the "lower" part (the device part) of netdev
2. provide a well defined testing infrastructure for modules that utilise
   netdev
The actual tests that represent 1. are provided in the following commit
unittests: Provide unittests for net_dev_dummy

* tests if net_dev_dummy is correct and if driver part of net_dev is
  correct
Merge pull request #1731 from authmillenon/netdev-test-dummy

netdev: Provide test network device with netdev interface
Merge pull request #1824 from haukepetersen/fix_cortex_isrs

cpu: removed NAKED attribute from ISRs
core: refactor sched_run

`sched_run()` was cluttered. Many individual changes were done without a
proper refactoring.
Merge pull request #1817 from haukepetersen/add_driver_lps331ap

drivers: added driver for LPS331AP pressure sensor