Bind (*parse-bare-structs-as-pointers* t) when parsing function definitions

In parse-args-and-types, foreign-funcall-form,
foreign-funcall-varargs-form, bind 
(*parse-bare-structs-as-pointers* t) 
when parsing function definitions so that if a bare structure is
specified, the expanded form with have :pointer or (:pointer (:struct
foo)) and therefore the type will be correctly recognized.