SpriteFont should support UTF-8 strings

[walbourn]

There is momentum to adopting UTF-8 Everywhere which currently makes a it a little difficult to work with SpriteFont that uses wchar_t. The library should be updated with DrawString, MeasureString, and MeasureDrawBounds overloads that take char assuming it's UTF-8 (not ASCII or some other codepage).

[walbourn]

For now the workaround is to do the conversion in your app:

wchar_t temp[1024] = {};
int result = MultiByteToWideChar(CP_UTF8, 0, char-string, -1, temp, _countof(temp));
if (!result)
    throw std::exception("MultiByteToWideChar"):

// Use temp to call SpriteFont->DrawString

[walbourn]

Fixed in this pull request