#174 ConvertToWide and ConvertToNarrow for string conversions

[Vidar Hasfjord]

Currently, we have a simple way to convert narrow and wide strings to owl::tstring using owl::to_tstring. It would be nice to have the converse functions ConvertToWide and ConvertToNarrow.

This would allow the deprecation of the string conversion macros. See [bugs:#486].

It would also simplify code that currently calls the low-level Windows API functions MultiByteToWideChar and WideCharToMultiByte.

See "Converting between narrow and wide strings" in "Strings in OWLNext".

[Vidar Hasfjord]

ConvertToNarrow and ConvertToWide have now been implemented in Owlet [r5381].

Specialisations to owl::from_tstring for std::string and std::wstring were added in Owlet [r5382]. These call ConvertToNarrow and ConvertToWide, respectively. See [feature-requests:#87/#03c0].

[Vidar Hasfjord]

This feature has now been implemented on the trunk [r5384].

[Vidar Hasfjord]

ConvertToNarrow and ConvertToWide has been reimplemented in Owlet [r6470] to fix conversion issues [bugs:#486]. This fix was merged into the trunk [r6537].