ASDF-FLV -- Hack for ASDF to modify file propeties on a per file basis

Hack for ASDF to modify file propeties on a per file basis. Crudley based on Didier Verna's ASDF-FLV.

  (asdf:defsystem "foo"
    :serial t
    :components ((:file "zork" :properties ((:base 8.) (:package "SI")))))

Currently supported propety names:

  :IBASE 	Sets *READ-BASE* when loading/compiling.
  :BASE		Sets *PRINT-BASE* when loading/compiling.
  :READTABLE	Sets *READTABLE* when loading/compiling.
  :PACKAGE	Sets *PACKAGE* when when loading/compiling.