Replace delete-selection properties on commands with a function check for strict mode #738
Description
Expected behavior
When in strict mode and delete-selection-mode is enabled, we should not allow supersede to kill imbalanced regions.
Actual behavior
With strict mode on no checks are performed when using sp-backward-delete-char and friends to kill a region, only when calling sp-delete-region or sp-kill-region.
Steps to reproduce the problem
Enable strict mode and use some of the abovementioned commands to kill imbalanced region.