Darwin-based host patches

- Remove various build warnings
- Fix building with modules on macOS
- Fix mouse/keyboard GUI interactions

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# gpg: Good signature from "Philippe Mathieu-Daudé (F4BUG) <f4bug@amsat.org>" [unknown]
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* tag 'darwin-20220315' of https://github.com/philmd/qemu

: (21 commits)
  MAINTAINERS: Volunteer to maintain Darwin-based hosts support
  ui/cocoa: add option to swap Option and Command
  ui/cocoa: capture all keys and combos when mouse is grabbed
  ui/cocoa: release mouse when user switches away from QEMU window
  ui/cocoa: add option to disable left-command forwarding to guest
  ui/cocoa: Constify qkeycode translation arrays
  configure: Pass filtered QEMU_OBJCFLAGS to meson
  meson: Log QEMU_CXXFLAGS content in summary
  meson: Resolve the entitlement.sh script once for good
  osdep: Avoid using Clang-specific __builtin_available()
  audio: Rename coreaudio extension to use Objective-C compiler
  coreaudio: Always return 0 in handle_voice_change
  audio: Log context for audio bug
  audio/dbus: Fix building with modules on macOS
  audio/coreaudio: Remove a deprecation warning on macOS 12
  block/file-posix: Remove a deprecation warning on macOS 12
  hvf: Remove deprecated hv_vcpu_flush() calls
  hvf: Make hvf_get_segments() / hvf_put_segments() local
  hvf: Use standard CR0 and CR4 register definitions
  tests/fp/berkeley-testfloat-3: Ignore ignored #pragma directives
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>