[9] RFR (XS): 8071787: Don't block inlining when DONT_INLINE_THRESHOLD=0

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/8071787/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8071787

For testing & performance measurements, sometimes it's useful to replace 
block inlining wrappers with trivial reinvokers.

This change extends DONT_INLINE_THRESHOLD in the following manner:
   DONT_INLINE_THRESHOLD = -1: no wrapper
   DONT_INLINE_THRESHOLD =  0: reinvoker
   DONT_INLINE_THRESHOLD >  0: counting wrapper

Before that DONT_INLINE_THRESHOLD=0 meant a counting wrapper which is 
removed on the first invocation. After the change, it's 
DONT_INLINE_THRESHOLD=1.

Testing: manual, java/lang/invoke

Best regards,
Vladimir Ivanov