Cristian Adam authored Nov 14, 2019 and Brad King committed Nov 14, 2019

Fix logic added by commit 81566557 (ObjC: Initialize ObjC/XX standard
properties from C/C++ counterparts, 2019-11-09) to account for cases
when the CXX standard is not explicitly set.  Also, do not copy the
`*_STANDARD_REQUIRED` and `*_EXTENSIONS` properties unless we copied the
`*_STANDARD` property.