Fixes #2367, closes #2467 - Use the check when using delegation for mouseenter.

Since 1.4.2 the native mouseenter/mouseleave events are used, when available
(Firefox, IE). For delegation however, it should has to use mouseover/mouseout
because it should still fire each time an element is entered or left so it can
check if it matches the selector.

thanks @luisateixeira for the research/fix
Merge branch 'fix-2367'
use native getComputedStyle on IE9 and IE10 instead of non-standard currentStyle
Add <opera> packager block
Merge branch 'refactor_getComputedStyle' closes #2419
Mozilla has long ago renamed MDC to MDN
Merge pull request #2483 from gonchuki/change_MDC_to_MDN

Mozilla has long ago renamed MDC to MDN