[omniORB] Preprocessor check for value type support

[Peter S. Housel]

Unless I missed it, there doesn't seem to be a preprocessor #define that
would allow determining whether or not value types are supported, i.e.,
that would distinguish between omniORB 4.0.x and 4.1.x.  Such a #define
would be useful for things such as the CORBA::omniORB Perl module, to
determine whether or not the bindings are able to support value types
while allowing compilation on both 4.0.x and 4.1.x.

-- 
Peter S. Housel <housel at acm.org>