Attacking unanchored windows with a wrench turns them into stacks of glass

Functionality
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* You can turn unanchored windows (ones that you can pull and push) back into panes of glass by attacking with a wrench. It makes no sense that the construction of a window is a one way process. Currently you can achieve this by smashing the window then welding the glass back together.

Code changes:
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* Added an "if istype(wrench)" condition to attackby for windows that drops one or two sheets of glass or reinforced glass based on the type of window. Only if the window is not anchored.