RFR(M): 8213528: fp registers should not need to be saved around a CallLeafNoFP

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8213528/webrev.00/

Currently CallLeafNoFP and CallLeaf don't differ in any way. My
understanding is that CallLeafNoFP should give the guarantee that it
leaves fp registers untouched and so fp registers shouldn't be saved
around a CallLeafNoFP. That's what this change implements. To be on the
safe side, all CallLeafNoFP calls are turned into CallLeaf and existing
behavior is preserved. That's another change motivated by Shenandoah
where we have a use for this.

Roland.