[Mac] Add a testing shim for secure event input functions
        https://bugs.webkit.org/show_bug.cgi?id=116122

        Reviewed by Mark Rowe.

        Added a new target with a dynamic library that interposes secure event input functions.
        We need this to avoid interfering with user session state.

        * Configurations/WebCoreTestShim.xcconfig: Added.
        * WebCore.xcodeproj/project.pbxproj:
        * platform/mac/DynamicLinkerInterposing.h: Moved from Source/WebKit2/Shared/mac/DyldInterpose.h.
        * testing/WebCoreTestShimLibrary.cpp: Added.
        (shimEnableSecureEventInput):
        (shimDisableSecureEventInput):
        (shimIsSecureEventInputEnabled):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150089 268f45cc-cd09-0410-ab3c-d52691b4dbfc