Sortable: Horizontal lists with inline-block items

Sortable: Added inline-block to the floating calculation when determining whether items are being displayed horizontally. Related to #6702 - horizontal sortable not working (and solution)

This is an addon to michaelmwu's fix brought up in the #6702 ticket and merged as this commit 20b010640e837cad1ad7203e02b28b399e328725