Fix finding cursor position in words with accents

In positionInLigature() we were mixing indexes into the script item with
indexes into the entire string. The getClusterLength() function would expect
an attributes array for the current script item and it thus needs to be
adjusted by si->position. In addition, when looking for the next grapheme
boundary, we were comparing pos (which indexed the string) with end (which
indexed the script item). This has also now been fixed by adjusting for
si->position as well.

Task-number: QTBUG-30123
Change-Id: Id02e2eddcc5b7888eacb34bd1e39cc6911880ca1
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
Use Q_UNLIKELY in qCDebug, qCTrace

By default debug, trace is disabled, so this can be marked as unlikely.

Change-Id: I221a688c953c1ff1fdfda65d2d99457785d3ff47
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Test that Qt tools can handle ' as a digit separator.

Change-Id: I0a3446d02184989c32367e66d4f5d9e464a56ec6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>