Remove the extra margins when checking owner drawn menu icons size.

Remove the extra margins when checking owner drawn menu icons size.

The extra +4 in IsLessThanStdSize() functions resulted in assert failures
under Windows XP after the ownerdraw drawing changes so remove it as nobody
knew why was it there anyhow.

Also replace IsLessThanStdSize() with IsGreaterThanStdSize() to allow using it
directly instead of always testing for !IsLessThanStdSize().

See #11657.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64088 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775