JDK 9 RFR of JDK-8157724: Improve javadoc tag usage in java.math

[joe darcy]

Hello,

The javadoc of the java.math package has various locations where the 
@jls, @apiNote, etc. javadoc tags could be used. Those tags should be 
used as appropriate. Please review the webrev below which makes those 
updates along with some typo fixes:

     http://cr.openjdk.java.net/~darcy/8157724.0/

Thanks,

-Joe