Replicate Numeric.log changes in Cool.log

(why is all of this stuff duplicated like this? Cool really just does a
coersion to Numeric for all of these mathematical methods and
maintaining docs for them in 2 places is LTA)

doc/Type/Cool.pod6

@@ -529,7 +529,8 @@ Coerces the arguments (including the invocant in the method form) to
 L<Numeric|/type/Numeric>, and returns its
 L<Logarithm|https://en.wikipedia.org/wiki/Logarithm> to base C<$base>, or to
 base C<e> (Euler's Number) if no base was supplied
-(L<Natural logarithm|https://en.wikipedia.org/wiki/Natural_logarithm>.
+(L<Natural logarithm|https://en.wikipedia.org/wiki/Natural_logarithm>).
+Returns C<NaN> if C<$base> is negative. Throws an exception if C<$base> is C<1>.
 
     say (e*e).log;              # 2