core: imply current_prio in `sched_switch()`

There is no need to supply the current priority to `sched_switch()`,
when this function can easily tell the value of
`active_thread->priority` itself.
tests: add missing license to test_struct_tm_utility
Merge pull request #1261 from Kijewski/test_struct_tm_utility-license

tests: add missing license to test_struct_tm_utility
pnet: accept should return a new generated file descriptor

From man page:
On success, these system calls return a nonnegative integer that is a
descriptor for the accepted socket. On error, -1 is returned, and errno
is set appropriately.
Merge pull request #1262 from cgundogan/fix_posix_accept

pnet: accept should return a new generated file descriptor
Merge pull request #1057 from Kijewski/sched_switch-current_prio

core: imply current_prio in `sched_switch()`
license checker WIP
set exit code AND use UNKNOWN
 assign UNKNOWN a more sensible default
remove stale license patterns
fix 3c-BSD-clark license pattern
patterns/1c-BSD -> patterns/1c-BSD-arm
remove useless doxygen command
fix 1c-BSD-arm
patterns/gplv2-v1 -> patterns/gplv2-pjrc