Add with-foreign-place macro

[Luís Oliveira]

by lichteblau: http://paste.lisp.org/display/112543

CL-USER> (defmacro with-foreign-place ((name type) &body body)
           (let ((ptr (intern (format nil "&~A" (symbol-name name))
                              (symbol-package name))))
             `(cffi:with-foreign-object (,ptr ,type)
                (symbol-macrolet ((,name (cffi:mem-ref ,ptr ,type)))
                  ,@body))))
WITH-FOREIGN-PLACE

;; then you could write:

CL-USER> (with-foreign-place (object :pointer)
           (with-foreign-place (pointer :pointer)
             (setf pointer &object)
             (function-that-takes-a-pointer-to-pointer &pointer)))