SRFI-144: accept zero arguments for flmax/flmin

SRFI-144 requires that (flmin) returns +inf.0 and that
(flmax) returns -inf.0, so these procedures can't really
be aliases to the Chibi implementation of R7RS max and min.

lib/srfi/144/flonum.scm

@@ -17,8 +17,8 @@
 (define fl- -)
 (define fl* *)
 (define fl/ /)
-(define flmax max)
-(define flmin min)
+(define (flmax . args) (if (null? args) -inf.0 (apply max args)))
+(define (flmin . args) (if (null? args) +inf.0 (apply min args)))
 (define (flabsdiff x y) (abs (- x y)))
 (define flnumerator numerator)
 (define fldenominator denominator)