Request for review: 7124543 [macosx] Horizontal scrolling doesn't work

[Sergey Bylokhov]

Hi Everyone,
- Now we take into account native horizontal scroll event and invert the 
SHIFT modifier state.
- scrollAmount was changed from 3 to 1 to be closer to apple jdk 6.
- small cleanup.

Bug: http://monaco.sfbay.sun.com/detail.jsf?cr=7124543
Webrev can be found at: http://cr.openjdk.java.net/~serb/7124543/webrev.00/

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Best regards, Sergey.