QRegExp::escape() does not escape hyphen character even it has a special meaning inside square brackets.
For example, I want to search for 3 characters, 'a', '-' and 'b'. The regexp string "[a-b]" won't work, because in this context the hyphen has a
special meaning. Of course [ab-] or [-ab] will work but when the search pattern is created dynamically would be nice to use escape function.