Add an EdkDxeRuntimeSalLib that provide a SalLib that is safe for runtime use. The EdkDxeSalLib is now a boot service only lib.
Move the registration and processing of ExitBootServicesEvents() from the RuntimeLib to the UEFI DriverEntryPointLib in the MdePkg.
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@2057 6f19259b-4bc3-4df7-8a09-765794883524