Deprecate U_NO_THROW and U_NOEXCEPT and replace instances with real "noexcept" keyword
Since we require C++11 compilers, we should remove this old macro and use the actual "noexcept" keyword throughout ICU.
We use a lot of macros like these in ICU header files. I can’t actually think of a good reason to remove this one. U_NOEXCEPT works fine. I’ll instead reduce the scope of this bug to just replace the implementation of U_NO_THROW to be the same as U_NOEXCEPT.
Removing myself as reviewer, as there appears to be nothing to review at this time.