RFR(XS) : 8031115 : intrinsics for Math.decrementExact(J) and incrementExact(J) don't work

[Igor Ignatyev]

Hi all,

Please review patch.

Problem:
intrinsics _decrementExactL and _incrementExactL have 
long2_long_signature instead of long_long_signature

webrev: http://cr.openjdk.java.net/~iignatyev/8031115/webrev.00/
jbs: https://bugs.openjdk.java.net/browse/JDK-8031115
testing: failing tests 
(compiler/intrinsics/mathexact/sanity/DecrementExactLongTest.java and 
IncrementExactLongTest.java)

-- 
Igor