Fix race condition bugs when reading and writing to message buffers (#264)

* Fix inaccuracies in prvWriteBytesToBuffer description

* Perform atomic message write in prvWriteMessageToBuffer

* Remove unnecessary length arg from prvReadMessageFromBuffer

* Perform atomic message read in prvReadBytesFromBuffer

* Apply SpacesAvailable() fix

Original author: RichardBarry

* Apply review feedback

* Edit some prv functions for simplicity and consistency

- prvWriteMessageToBuffer
- prvReadMessageFromBuffer
- prvWriteBytesToBuffer
- prvReadBytesFromBuffer

* Significant simplification of prvWriteMessageToBuffer

* fixup off-by-one comment indentation

Co-authored-by: alfred gedeon <[email protected]>
Co-authored-by: RichardBarry <[email protected]>

Author: 3 people