RFR (S): 8228858: Reimplement JVM_RawMonitors to use PlatformMutex

[David Holmes]

bug: https://bugs.openjdk.java.net/browse/JDK-8228858
webrev: http://cr.openjdk.java.net/~dholmes/8228858/webrev/

A JVM_RawMonitor  (not to be confused with JvmtiRawMonitor) is a simple 
mutex (despite the name) currently implemented via two special entry 
points in the VM Monitor code. This fix changes that so that a 
JVM_RawMonitor is just a PlatformMutex, enabling us to delete the 
special Monitor code.

There are two clients of JVM_RawMonitor:
- the native Zip library provided by the JDK and used by the JVM during 
classloading
- AWT debug code

The first should be tested by using the VM. :) The second I don't know. 
But the functionality we're testing is already present so there's 
sufficient coverage just by testing one client.

Testing: tiers 1 - 3 on Linux/macOS/Window x64, Solaris sparcv9

Thanks,
David