[Installer] Change default setting for ARC from being disabled via
CLANG_ENABLE_OBJC_ARC='NO' on a project basis with -fobjc-arc for each
file to enable ARC on a project basis with CLANG_ENABLE_OBJC_ARC='YES' and using -fno-objc-arc for each file in pods that don't require ARC
[Changelog] Update changelog with changes regarding ARC
Merge pull request #2769 from k0nserv/master

Change default to use ARC and specify on per file basis if it's disabled.