osxvideo: fix mac os 10.14 build

lockFocusIfCanDraw is deprecated in mac os 10.14.  Apple suggests a
different way to do what that does, but for now, just suppress the deprecation.

There's no way to disable just that deprecation, so shut them all down.

OpenGL is also deprecated in mac os 10.14.  There is a gentle way to
turn off just those deprecations (GL_SILENCE_DEPRECATION), but since
this commit turns them all off, that's moot.

gstreamer/gst-plugins-good#577
13 jobs for issue577-minimal in 56 minutes and 50 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Preparation
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gst indent

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manifest

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  Build
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build fedora x86_64

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build nodebug fedora x86_64

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  Test
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check fedora

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integration testsuites fedora

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  Full Builds
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build cerbero android universal

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build cerbero cross win32

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build cerbero cross win64

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passed #223157
build cerbero fedora x86_64

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  Full Tests
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valgrind bad

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passed #223161
valgrind good

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  Apps
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android universal examples

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