Removes the property named
propertyname from the property list named
if it exists.
If REMPROP removes the final property from a property list, then the property list may be erased.
plistname input must be a word.
propertyname input may be word, list, or array.
Property names are compared in the same manner as EQUALP compares its inputs.
PPROP "plist1 "p1 1 PPROP "plist1 "p2 2 SHOW PLIST "plist1[p2 2 p1 1]
REMPROP "plist1 "p1 SHOW PLIST "plist1[p2 2]