Java-style iterators are slower than STL-style ones, so
they should not be used in library code.
Replaced them with C++11 range-for, STL iterators or, in
one case, qDeleteAll().
In one case, avoid a double hash lookup by using erase(it)
instead of remove(it.key()), which we can now do without
detaching, due to the new erase() taking const_iterator.
Change-Id: I96174657fed70f76120b2c9d8190b4e70d5d8179
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
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