RFR: Back out: Avoid stub when calling to write-barrier from C2, remove all related code

[Roman Kennke]

This patch breaks C1 and interpreter because they might also use xmm
registers. At the very least, we need to put our register saving code
back in. We need to consider what to do with C2.

I'll do the exact reverse of:
http://cr.openjdk.java.net/~rkennke/remove-c2-wb-stub/webrev.02/

using "hg backout"

Testing: tier3_gc_shenandoah

Roman