- Also refactored internals to use weak/shared pointers

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.

When passing in valid data with zero size, replaceWith() will do nothing and leave the MemoryBlock in its previous state which may be unexpected. replaceAll() will reset the MemoryBlock and resize it to 0