MIDI only plugins are no longer provided valid audio buffers
Graph nodes are only executed when they have active connections

When plugins change their 'parameter info' this often means that their
previous parameter text is no longer valid, so we should fetch new text
to represent the parameter value.

This change was primarily tested with Kontakt.

Adds a mechanism to notify the host that the plugin state needs saving,
using updateHostDisplay.

Also allows JUCE hosts to detect when a plugin needs its state saving
via the AudioProcessorListener.

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.

The AAX SDK already checks for truncated IDs internally. If any ID is
truncated, details will be written to Pro Tools' log file (you may need
to enable logging first). Search for "AAX_ASSERT" in the log to find
triggered assertions.

This fixes warnings that are emitted when building with the `-analyze`
flag enabled.