Remove usage of toAscii/fromAscii (basically replace with toLatin/fromLatin)
also:
- use implicit conversion from toLatin1-QByteArray to const char*, where possible
- constData() instead of data() everywhere, to avoid unneeded deep copies if code get copied
- removed unneeded conversion to latin1 where QString was expected
- use QByteArray instead of QString, if QString not really needed
- cache result of conversion where useful
REVIEW: 107871
Thanks boud and jarosław for review