In face of the backlash on asdf-devel@ and pro@, rename :DBG back to DBG.
Remove the controversial DBG macro altogether.

Its place is another library, in the keyword package,
or using (uiop-debug), in the current package.
More tweaks and cleanups for GCL.
Bump version to 3.1.0.18
More cleanups for GCL support.
Bump version to 3.1.0.19
UIOP: enhance ensure-pathname, add docstrings, fix getcwd on abcl (?)
Bump version to 3.1.0.20