Ugly style-warning from defmethod close

I get an ugly style-warning whenever I load a (defmethod close
((stream whatever-stream) &key abort) ...). It complains that an
earlier ftype proclamation is clobbered (see below). Affected systems
are for example chunga and flexi-streams.

I believe that it comes from the fact that the "original" close
/function/ is replaced by a generic function in gray-streams.lisp, but
its inferred ftype is not removed. This might be fixed by giving an
appropriate ftype declamation in gray-streams.lisp.

Minimal test:

CL-USER> (defclass my-stream (stream)
           (foo))
#<STANDARD-CLASS MY-STREAM>
CL-USER> (defmethod close ((stream my-stream) &key abort)
           (close stream :abort abort))
STYLE-WARNING:
   Generic function CLOSE clobbers an earlier FTYPE proclamation
   (FUNCTION (STREAM &KEY (:ABORT T)) (VALUES (MEMBER T) &OPTIONAL)) for
   the same name with (FUNCTION (T &KEY (:ABORT T)) *).
#<STANDARD-METHOD SB-GRAY::PCL-CLOSE (MY-STREAM) {C222699}>
CL-USER>

sbcl --version: SBCL 1.0.51

uname -a: Linux alraune 2.6.34-tuxonice-r6alraune #3 SMP Mon Jan 3
00:16:24 CET 2011 i686 Pentium(R) Dual-Core CPU T4200 @ 2.00GHz
GenuineIntel GNU/Linux

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 :COMMON-LISP :SBCL :SB-DOC :SB-PACKAGE-LOCKS :SB-UNICODE :SB-EVAL
 :SB-SOURCE-LOCATIONS :IEEE-FLOATING-POINT :X86 :UNIX :ELF :LINUX :SB-THREAD
 :LARGEFILE :GENCGC :STACK-GROWS-DOWNWARD-NOT-UPWARD :C-STACK-IS-CONTROL-STACK
 :COMPARE-AND-SWAP-VOPS :UNWIND-TO-FRAME-AND-CALL-VOP :RAW-INSTANCE-INIT-VOPS
 :STACK-ALLOCATABLE-CLOSURES :STACK-ALLOCATABLE-VECTORS
 :STACK-ALLOCATABLE-LISTS :STACK-ALLOCATABLE-FIXED-OBJECTS :ALIEN-CALLBACKS
 :CYCLE-COUNTER :INLINE-CONSTANTS :MEMORY-BARRIER-VOPS :MULTIPLY-HIGH-VOPS
 :LINKAGE-TABLE :OS-PROVIDES-DLOPEN :OS-PROVIDES-DLADDR :OS-PROVIDES-PUTWC
 :OS-PROVIDES-BLKSIZE-T :OS-PROVIDES-SUSECONDS-T :OS-PROVIDES-GETPROTOBY-R
 :OS-PROVIDES-POLL)