Floating infinities crash EQUALP hash-table

[Douglas Katzman]

* (setf (gethash sb-ext:single-float-positive-infinity (make-hash-table :test 'equalp)) 1)
debugger invoked on a SIMPLE-ERROR in thread
#<THREAD "main thread" RUNNING {1001FDEA73}>:
  can't decode NaN or infinity: #.SB-EXT:SINGLE-FLOAT-POSITIVE-INFINITY

* (setf (gethash sb-ext:double-float-positive-infinity (make-hash-table :test 'equalp)) 1)
debugger invoked on a SIMPLE-ERROR in thread
#<THREAD "main thread" RUNNING {1001FDEA73}>:
  Can't decode NaN or infinity: #.SB-EXT:DOUBLE-FLOAT-POSITIVE-INFINITY.

* (setf (gethash sb-ext:single-float-negative-infinity (make-hash-table :test 'equalp)) 1)
debugger invoked on a SIMPLE-ERROR in thread
#<THREAD "main thread" RUNNING {1001FDEA73}>:
  can't decode NaN or infinity: #.SB-EXT:SINGLE-FLOAT-NEGATIVE-INFINITY

* (setf (gethash sb-ext:double-float-negative-infinity (make-hash-table :test 'equalp)) 1)
debugger invoked on a SIMPLE-ERROR in thread
#<THREAD "main thread" RUNNING {1001FDEA73}>:
  Can't decode NaN or infinity: #.SB-EXT:DOUBLE-FLOAT-NEGATIVE-INFINITY.

The root cause is a FLOOR operation in HASH-FLOAT in NUMBER-PSXHASH.