[PATCH] Mark move constructors as "noexcept"

[Tom Tromey]

>>>>> "Tom" == Tom Tromey <tromey@adacore.com> writes:

Tom> I recently learned that move constructors generally should be marked
Tom> "noexcept".  This ensures that standard containers will move objects
Tom> when possible, rather than copy them.

Tom> This patch fixes the cases I could find.  Note that implicitly-defined
Tom> or defaulted move constructors will automatically do what you'd
Tom> expect; that is, they are noexcept if all the members have noexcept
Tom> move constructors.

Tom> While doing this, I noticed a couple of odd cases where the move
Tom> constructor seemed to assume that the object being constructed could
Tom> have state requiring destruction.  I've fixed these as well.  See
Tom> completion_result and scoped_mmap.

I'm checking this in.

Tom