[dev-context] Local settings for frame borders

Hi, Currently it is not possible to individually set the thickness of the different borders of a frame. A typical use-case is typesetting a table row where the top frame is double the thichness of the bottom frame. Having to resort to metapost for something as simple as this is a bit annoying. Attached is a metapost library that defines "local" fences and allows you to set border individually. For example \defineframed[...][frame=off, topframe=local, topframethickness=1pt, bottomframe=local, bottomframethickness=0.5pt] sets the top frame to be 1pt and the bottomframe to be 0.5pt. Does it make sense to include this (appropriately modified) in the core? Or is it better to distribute such enhancements as a user module. Aditya