Prior to this fix a data race could occur on 
ARAAudioSourceReader::hostReader between the functions 
didEnableAudioSourceSamplesAccess() and readSamples().

This is a breaking change - see BREAKING-CHANGES.txt

This commit replaces the contents of the flac directory with the
unchanged contents of the flac_134 directory.

read() now returns failure in the case of a read timeout, or if
reading any block failed.

This commit removes the various compiler-specific JUCE_DEPRECATED macros and replaces them with C++14's deprecated attribute. It also removes the JUCE_CATCH_DEPRECATED_CODE_MISUSE flag as we can rely on the override specifier catching usage of these old virtual methods, and tidies up the DOXYGEN preprocessor checks as they were inconsistent across the codebase.