Bug 849657 patch 1: Expose CSS_PROP_PUBLIC_OR_PRIVATE macro to users of nsCSSPropList.h rather than CSS_PROP_DOMPROP_PREFIXED, so that we can avoid 'CssFloat' spreading even further.  r=bzbarsky
Bug 849657 patch 2: Change internal uses of 'CssFloat' to 'Float'.  r=bzbarsky