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#1569 — Add regexp tests for resetting capture groups

See email below from Paul Ruizendaal:

The expression /((a)|(aa))b/.exec('aab') should result in ['aab','aa',undefined,'aa']. The key here is that the 2nd capture gets reset when the left alternative is abandoned. In the spec algorithm this is automatic, as States are "copy on write"; I think many implementations will use a "save & restore" policy and then this then needs to be verified.

This is not covered by test262, but it is by the mozilla suite test "ecma_3/RegExp/regress-31316.js".

Recommend to add the following test to section

function test() {
var rc = /((a)|(aa))b/.exec('aab');
return !rc[2];