[class.copy]p23: Fix an assertion caused by incorrect argument numbering in a
diagnostic, add a test for this paragraph, and tighten up the diagnostic wording
a little.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@155784 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed