wireshark: fix dissector plugin and expand documentation

The wireshark dissector plugin currently fails with a "Lua Error" when
trying to parse nativenet packets. This patch restores working behaviour
by commenting the offending line introduced in 1258675, which intention
was to account for padding in small packets. It further adds a comment
on how to edit the plugin for the case padding information is required.

The README.md now contains a usage note for configuration on fedora
which might also be helpful for users of other distributions.
destiny: wireshark compliant tcp flags
This enum is also used to set the tcp flags within a tcp header.
With the current values in this enum, wireshark is not able to
recognize the tcp segments as their actual tcp type,
and thus odd messages in wireshark appear.

destiny: reusing tcp flags for combinations
destiny: fixed condition for error handling
send_tcp returns either the length of the sent data,
or -1, if an error was detected.

The current implementation checks for != 1.
This results in executing the error case, although
there was semantically no error returned from send_tcp.
core/cortex-m: add missing NORETURNs to thread_arch
Merge pull request #1274 from sgso/wireshark_dissector

wireshark: fix dissector plugin and expand documentation
native: add id option
Merge pull request #1192 from LudwigOrtmann/native_override_pid

native: add id option
destiny: change byte order of ipv6_header->length
When accessing the length field of an ipv6_header a byte order switch (host -> network) is necessary.
Otherwise, it breaks calculations or the checksum and other tcp related computations.
Furthermore, when writing to ipv6_header->length it is important to switch this
from host byte order to network byte order.
destiny: using a bit field for tcp_header->data_offset is more convenient
In the current implementation the data offset is coded into an uint8_t.
Of this uint8_t only 3 bits apply for the data offset.
The remaining bits represent reserved flags for future use.
However, a proper bit masking is forgotten in order
to obtain the data offset part of this uint8_t.

Therefore, defining this uint8_t as a bit field allows a more convenient
method of access.
Merge pull request #1275 from cgundogan/fix_tcp_flags_for_wireshark

destiny: wireshark compliant tcp flags
Merge pull request #1300 from cgundogan/fix_wrong_byte_order_ipv6_length

destiny: change byte order of ipv6_header->length
Merge pull request #1292 from Kijewski/issue-1288

core/cortex-m: add missing NORETURNs to thread_arch
core/include/arch/irq_arch.h: fix typo and trailing whitespaces
Merge pull request #1308 from N8Fear/fix-typo-and-whitespaces

core/include/arch/irq_arch.h: fix typo and trailing whitespaces
cpu: renamed cortexm_common->cortex-m3_common and cleanup
pnet: silence unused argument warnings
Merge pull request #1295 from haukepetersen/mv_cpu_cortexm-common

cpu: renamed cortexm_common->cortex-m3_common and cleanup
Merge pull request #1312 from mehlis/pnet-unused-param

pnet: silence unused argument warnings
cpu:cortex_common: add core_panic function
Merge pull request #1313 from thomaseichinger/cortexm_crash

cpu:cortex_common: add core_panic function