Remove JSC_OBJC_API_AVAILABLE_MAC_OS_X_1080

Remove JSC_OBJC_API_AVAILABLE_MAC_OS_X_1080
https://bugs.webkit.org/show_bug.cgi?id=145403

Reviewed by Anders Carlsson.

JSC_OBJC_API_AVAILABLE_MAC_OS_X_1080 was used to enable the JavaScriptCore Objective-C API
for WebKit and Safari projects building with JavaScriptCore targeting OS X 10.8. We don’t
need it anymore.

* API/JSBase.h:
* API/JSContext.h:
* API/JSManagedValue.h:
* API/JSValue.h:
* API/JSVirtualMachine.h:
* Configurations/Base.xcconfig:
* postprocess-headers.sh:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@184906 268f45cc-cd09-0410-ab3c-d52691b4dbfc