RFR (S): 8220368 : Update String.indexOf to test all the C2 intrinsics

[eric.caspole at oracle.com]

Hi everybody,

Could I have reviews on this update to the String.indexOf JMH adding 
several new benchmarks so as to test all the intrinsics of Latin1 and 
UTF-16:

   _indexOfIL
   _indexOfIU
   _indexOfIUL
   _indexOfL
   _indexOfU
   _indexOfU_char
   _indexOfUL

These should be helpful in testing updates from Graal and performance 
regression testing in general.

JBS:

https://bugs.openjdk.java.net/browse/JDK-8220368

Webrev:

http://cr.openjdk.java.net/~ecaspole/JDK-8220368/01/webrev/


Thanks,

Eric