Description:
------------
PHP messes up coordinates for <input type="image" .. fields when fieldname is not simple one level name but multilevel name.
For example name="smth[field]" is easy way to test it

Reproduce code:
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<form action="" method="GET"><input type="image" name="smth[imgsubmit]" src="t.jpg" width="200" height="200"></form>
<?php
print_r($_POST);
?>


Expected result:
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Since single level image submits end up in post and get arrays as
fieldname_x and fieldname_y I would expect above code to produce GET array as such:
Array ( [smth] => Array ( [imgsubmit_y] => 80, [imgsubmit_x] => 80 ) )

or even better would be actually
Array ( [smth] => Array ( [imgsubmit] => Array([x] => 80, [y] => 80) ) )

but it woul be a breaking change when changed to that and would be inconsistent with single level fields, but also it would be much clearer and would not prohibit me from having <input type="image" name="someimage" src="..."> and <input type="hidden" name="someimage_x" value="previousvalue"> fields on same form at the same time

Actual result:
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Array ( [smth] => Array ( [imgsubmit] => 80 ) )