RFR (XS): 8003879: Duplicate definitions in vmStructs

[Mikael Vidstedt]

Please review the below change.

The change for 7045397 introduced a couple of duplicate entries in the 
vmStructs::localHotSpotVMTypes array. This shows up when using the jmap 
tool in a rather ugly way:

Attaching to process ID 25561, please wait...
Warning: the type "MetablockTreeDictionary" (declared in the remote VM 
in VMStructs::localHotSpotVMTypes) had its size declared as 32 twice. 
Continuing.
Warning: the type "AFLBinaryTreeDictionary" (declared in the remote VM 
in VMStructs::localHotSpotVMTypes) had its size declared as 32 twice. 
Continuing.
Debugger attached successfully.

It does appear like jmap works despite this, but clearly it's annoying 
at a very least to get the warnings.

In addition to removing the two duplicated entries I also added a 
simple, naive runtime test to walk through and make sure no type is 
repeated. The VMStructs::init only called in debug_only so there's no 
startup overhead in product, but it may be better to turn the test into 
a unit test and only running it as part of ExecuteInternalVMTests. 
Feedback appreciated!

http://cr.openjdk.java.net/~mikael/8003879/webrev.00/

Cheers,
Mikael