[13u] RFR: 8226721 : Missing intrinsics for Math.ceil, floor, rint

[Sergey Nazarkin]

Hi!

Please review a set of backports to bring math intrinsic to jdk13. The train consists of initial commit (8226721) and build fix for x86 (8231713) 

Original records
https://bugs.openjdk.java.net/browse/JDK-8226721 (initial)
https://bugs.openjdk.java.net/browse/JDK-8231713 (x86 build fix)

The patch from 8226721 applies mostly cleanly except one small part at x86.ad due to context shift by missed 8224974. The second part (8231713) applies cleanly. 

Webrev 
http://cr.openjdk.java.net/~snazarki/webrev/8226721/