Reserved keywords for later use [attn: Walter]

[Jeff]

I dare say there are certain features conceived for later versions of 
the D specification that would require - or at least greatly benefit 
from - additional keywords.

Obviously some of these features might not ever see the the light of day 
for various reasons, but I think it could be wise to reserve keywords 
related to likely future language features before the 1.0 spec is 
reached to avoid the risk of breaking code in future versions.

I'm aware that some are already reserved, but does it seem reasonable to 
try to find as many as possible that are likely to be needed later and 
reserve them now?