Fixed a typo in the HTML5 form externs

I could find any evidence of a lower case only form.novalidate property, it is form.noValidate.
Added boxShadow to the CSSOM externs

The CSS 3 box shadow CSSOM property was not defined in the externs for some reason.
Added MozBoxShadow to the externs

For completeness.
Merge pull request #623 from phistuck/master

Updated and fixed some externs