handle temporaries which have been lifetime-extended to static storage duration
within constant expressions. This correctly handles nested lifetime extension
(through reference members of aggregates in aggregate initializers) but
non-constant-expression emission hasn't yet been updated to do the same.
llvm-svn: 183283
object x, x's subobjects can be constructed by constexpr constructor even if
they are of non-literal type, and can be read and written even though they're
not members of a constexpr object or temporary.
llvm-svn: 181506