If there is another thread holding a lock that the main thread wants to
take while pretending to be the IO thread, we will wait forever as we do
not move SITL time forward while pretending to be the IO thread.
This patch simply allows time to move forward if we've failed to take a
semaphore immediately and need to wait.
This commit changes the way libraries headers are included in source files:
- If the header is in the same directory the source belongs to, so the
notation '#include ""' is used with the path relative to the directory
containing the source.
- If the header is outside the directory containing the source, then we use
the notation '#include <>' with the path relative to libraries folder.
Some of the advantages of such approach:
- Only one search path for libraries headers.
- OSs like Windows may have a better lookup time.