RFR(S) : 8038186 : [TESTBUG] improvements of test j.l.i.MethodHandles

[Igor Ignatyev]

Hi all,

Please review the patch:

Problems:
- MethodHandlesTest::testCatchException() doesn't provide enough testing 
of j.l.i.MethodHandles::catchException().
- MethodHandlesTest contains more than 3k lines, an auxiliary code 
together w/ a test code, many methods aren't connected w/ each other, 
etc. All this leads to that it is very very hard to understand, maintain.

Fix:
- the auxiliary code was moved to testlibray
- the test code was moved to a separate subpackage
- random signature is used for target and handler
- added scenarios w/ different return types

webrev: http://cr.openjdk.java.net/~iignatyev/8038186/webrev.01/
jbs: https://bugs.openjdk.java.net/browse/JDK-8038186
-- 
Igor