Memory error when moving a cse::uri

[kyllingstad]

The following code has a potential memory error:

cse::uri u("/foo");
auto v = std::move(u);

The std::string_view objects that refer to the various URI components (scheme, authority, path, etc.) may point to invalid memory after this.

They are supposed to always point to the cse::uri's internal std::string buffer. However, due to the small string optimisation, where sufficiently small strings may be stored in the memory area occupied by the std::string object itself (typically on the stack), as opposed to a separate (heap) memory area, that buffer may move along with the cse::uri, invalidating the std::string_view objects.

I've run into this error on VS2017, but I would be surprised if it didn't happen on other platforms as well.