Small change needed to make QString_char16 and QString_QChar return -1
in this case, but other combinations already returns -1.
[ChangeLog][QtCore][Behavior Change] QString::indexOf(QChar) and
QString::indexOf(char16_t) now treat a negative start-position, from,
bigger than the string's size as invalid. It previously
clipped such start-positions to the start of the string, inconsistently
with other QString indexOf overloads.
Change-Id: Ic56c8a558bf40a94845c649647db569892d4df02
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
f9b867216b