Modifiable iterator, that also supports removal.
Usage example:
for (MIter iter = ids.iter(); iter.valid(); iter.advance()) {
if (testSomething(iter)) {
iter.remove();
continue; // Iterator may point to something else
}
}
Remove the object the iterator currently points to.
Note that, usually, the iterator will now point to a different object, very
often to the previous one (but this is not guaranteed!)
