RFR: 8185756: JShell has broken links in its documentation

[Jonathan Gibbons]

Please review the following minor fixes for some broken links in the 
JShell API documentation.

In all cases, a @link to a method needs to specify the parameter list, 
because of the existence of a like-named field, albeit one with private 
access.

JBS: https://bugs.openjdk.java.net/browse/JDK-8185756
Webrev: http://cr.openjdk.java.net/~jjg/8185756/webrev.00/

-- Jon