The Apple threading documentation [^1] says the following:

> The second argument to pthread_setschedparam is the desired policy,
  which can currently be one of SCHED_FIFO (first in, first out),
  SCHED_RR (round-robin), or SCHED_OTHER. The SCHED_OTHER policy is
  generally used for extra policies that are specific to a given
  operating system, and should thus be avoided when writing portable
  code.

This appears to differ from the policy semantics on Linux and BSD, where
FIFO and RR are both explicitly real-time policies.

Therefore, on Linux/BSD we only enable the RR policy if the requested
priority is 8 or higher. Meanwhile, on macOS, we map all thread
priorities (0 - 10) onto the RR policy with an appropriate priority.

[^1]: https://developer.apple.com/library/archive/documentation/Darwin/Conceptual/KernelProgramming/scheduler/scheduler.html

The Apple threading documentation [^1] says the following:

> The second argument to pthread_setschedparam is the desired policy,
  which can currently be one of SCHED_FIFO (first in, first out),
  SCHED_RR (round-robin), or SCHED_OTHER. The SCHED_OTHER policy is
  generally used for extra policies that are specific to a given
  operating system, and should thus be avoided when writing portable
  code.

This appears to differ from the policy semantics on Linux and BSD, where
FIFO and RR are both explicitly real-time policies.

Therefore, on Linux/BSD we only enable the RR policy if the requested
priority is 8 or higher. Meanwhile, on macOS, we map all thread
priorities (0 - 10) onto the RR policy with an appropriate priority.

[^1]: https://developer.apple.com/library/archive/documentation/Darwin/Conceptual/KernelProgramming/scheduler/scheduler.html

Clang versions 5 to 8 inclusive seem to struggle to compile JUCE when
JUCE_BEGIN_NO_SANITIZE is used. This is unexpected, as simpler programs
using the same macro definitions compile correctly on clang 5.

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.

File::getContainerForSecurityApplicationGroupIdentifier will return the
path to a container which is shared between all apps using the specified
app group ID. This might be useful if you need to share resources
between a standalone app and an AUv3 plugin, for example.

The previous implementation would fail to open directories with names
that contained spaces, as the space would be escaped and then quoted.

I don't think it's particularly meaningful to supply parameters when
opening a file in this way (especially not quoting the parameters too!)
so I've removed that functionality.