RFR(s): 8025279 metaspace/flags/maxMetaspaceSize throws OOM: out of Compressed Klass space

[Mikael Gerdin]

Hi

Please review this small fix for throwing OutOfMermoryError with the 
correct cause string when failing to allocate a Klass.

The code incorrectly sets the cause string to "Compressed class space" 
if the allocation type is ClassType even if the VM is configured to not 
use a separate compressed class space.

The fix adds a helper function to determine if a MetadataType would be 
allocated in the compressed class space or not and uses that to figure 
out what string to send and which OOME to throw.

Webrev: http://cr.openjdk.java.net/~mgerdin/8025279/webrev.0
Bug link: https://bugs.openjdk.java.net/browse/JDK-8025279