remove warning: unused variables
fix warnings about signed/unsigned comparisons
fix warning about out of order initialization
remove warning about uninitialized variables
merge upstream/master > andrew/say-no-to-warnings
merge upstream/master into andrew/say-no-to-warnings

Conflicts:
	interface/src/ui/ApplicationOverlay.cpp
	libraries/audio/src/AudioRingBuffer.cpp
remove warning about signed/unsigned comparison
remove warnings about signed/unsigned comparisons
Merge pull request #3110 from AndrewMeadows/say-no-to-warnings

remove warnings