RFR: 8230827 javac gives inappropriate warning about potentially ambiguous methods

[Adam Sotona]

Hi,
I would like to ask for review of the patch fixing com.sun.tools.javac.comp.Comp:checkPotentiallyAmbiguousOverloads. The actual implementation is too strict and is warning about ambiguous methods even they differ in following parameters.
Plus I've created a test for ambiguous and non-ambiguous cases.

JBS: https://bugs.openjdk.java.net/browse/JDK-8230827
webrev: http://cr.openjdk.java.net/~asotona/8230827/webrev.00/

Mach 5 build with the patch passes all Tier 1 and Tier 2 tests. 
Several unrelated Tier 3 tests are actually failing.  


Thanks for the review,
Adam