RFR 8058089: api/javax_management/loading/MLetArgsSupport.html\#MLetArgsSupportTest0001 fails because of java.lang.IllegalArgumentException (argument type mismatch)

[Jaroslav Bachorik]

Please, review the following regression fix

Issue  : https://bugs.openjdk.java.net/browse/JDK-8058089
Webrev : http://cr.openjdk.java.net/~jbachorik/8058089/webrev.00

The regression was introduced by an en-mass update of new 
`Integer(param)` to `Integer.valueOf(param)`. For some reason in the 
MLet code only `param` was used instead of `Integer.valueOf(param)`. 
I've fixed this problem and also took the liberty to convert new Float() 
and new Double() to .valueOf(...) form. I also added a reg test 
asserting the correctness of param conversions performed by the MLet class.


Thanks,

-JB-