[Bug libstdc++/58338] Add noexcept to functions with a narrow contract

[bredelin at ucla dot edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58338

bredelin at ucla dot edu changed:

           What    |Removed                     |Added
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                 CC|                            |bredelin at ucla dot edu

--- Comment #10 from bredelin at ucla dot edu ---
It seems that these changes (see Sep 17th) also made the default constructor
explicit.  While this does follow the standard, it is the subject of this
defect report:

http://cplusplus.github.io/LWG/lwg-active.html#2193

Was this change intentional?