QRegExp WildcardUnix mode has bogus semantics

commit e7c36fc2 introduced the WildcardUnix mode.

first of all, the justification for that mode is bogus: even in "normal" glob mode, all wildcard characters can be escaped by simply putting them into square brackets. adding a new mode just adds confusion by giving people even more to learn instead of trying to understand what has worked for three+ decades. i'd immediately deprecate that mode again.

second, the handling of backslashes is broken: in the case '
' if (enableEscaping) if (isEscaping) branch, the isEscaping flag must be reset, not set again.
attached is a patch which should fix it. i leave (auto-)testing it to the author of that code.