Iostreams: Support filesystem3 paths. Refs #4485.
Based on Zhuo Qiang's patch with added tests and support
for operator=
.
I also used codecvt_type
to detect filesystem3::path
instead of string_type
. Using string_type
made
filesystem2::path
ambiguous because it has both
string_type
and external_string_type
members.
The member types are a bit arbitrary, but a more precise
distinction would probably also be more expensive.