changed parameters form `kernel_pid_t` to `int`
board/pca1000x: added/fixed dist scripts

- pca10000: added author to debug.sh
- pca10005: added debug and reset scripts
- pca10005: fixed flash script
- pca10005: adjusted env vars in Makefile.include
Fix thread_yield by avoiding the (too) early re-enablement of IRQ,
that is: before the newly selected thread's context is totally restored
Prevent the compiler to add an unwanted prologue in thread_yield()
Fix the race condition when an interruption occured at the beginning
of thread_yield(), i.e.: just after SR(R2) was pushed but before
the rest of the suspended thread's context was pushed!
unittests: make: Fix unittests for branch changes

Changing between branches in git typically leaves directories empty and
does not remove them. If you have different unittests in different
branches this leads to an error in building them, since the current
configuration expects a Makefile in all `tests-*` directory. This change
configures Make to search for a Makefile in `tests-*` rather than just
assuming that there is one.
Fixed comments
rpl: mute RPL

Removes all but one occurrence of printf and puts within routing (the
remaining puts is called from a debug function.
tests: don't build test/libfixmath on Travis CI

Very often the build unexplainably hangs.
Merge pull request #1648 from Kijewski/no-test-libfixmath

tests: don't build test/libfixmath on Travis CI
add backspace functionality in shell
Merge pull request #1561 from BytesGalore/fix_fd_parameter_warnings

sys/posix: changed parameters for `fd` from `kernel_pid_t` to `int`
transport_layer: Splitting UDP and TCP

Currently, the tcp and udp implementations are bound to each other in a
module called *destiny*. Thus, when using only one of them then the
other one gets also compiled into the binary and initialized,
which results in unnecessary RAM usage and workload for the CPU.

The approach in this PR defines a common module named *socket_base*,
which contains functions used by the posix layer. Compiled by it's own,
those functions return negative error codes, to symbolize upper layers
that they are not supported. When also including the modules *udp* or
*tcp* respectively, functions from *socket_base* get overwritten with the
correct functionality.

Defining *udp* or *tcp* in a Makefile also includes *socket_base*.
Defining *pnet* in a Makefile also includes *socket_base*.
Merge pull request #1508 from cgundogan/transport_layer_refactoring

transport_layer: Splitting UDP and TCP
drivers-lm75a: use sizeof array instead of reg_size
lint: reduce scope

Fix some lint warnings of kind
```
style (variableScope): The scope of the variable '…' can be reduced
```
cpu: lpc_common: reduce indentation level in iap.c
Merge pull request #1565 from Kijewski/scope

lint: reduce scope
Merge pull request #1618 from rousselk/msp430-fix-thread-yield

Fix thread_yield() on MSP430 platforms
example: adapt README to new naming of the transport layer