Enable WEB_AUDIO by default in the WebKit/mac port.

Enable WEB_AUDIO by default in the WebKit/mac port.
https://bugs.webkit.org/show_bug.cgi?id=68587

Reviewed by Simon Fraser.

Source/JavaScriptCore:

* Configurations/FeatureDefines.xcconfig:
* wtf/Platform.h:

Source/WebCore:

No new tests; existing webaudio/ layout tests cover this.

* Configurations/FeatureDefines.xcconfig:
* WebCore.xcodeproj/project.pbxproj: Add a build step which copies audio resources to
    the WebCore.framework bundle.

Source/WebKit/mac:

* Configurations/FeatureDefines.xcconfig:

Source/WebKit2:

* Configurations/FeatureDefines.xcconfig:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96526 268f45cc-cd09-0410-ab3c-d52691b4dbfc