SDWF 0.54 release

[Stewart Gordon]

I've revamped the internal imports, and so it now compiles under DMD 
0.163.  In the process, I've got rid of most public imports between 
modules - those that remain are in smjg.libs.sdwf.all and the new 
smjg.libs.sdwf.core.  So you might need to tweak your own imports so 
that your code still compiles.

And some stuff has been added to TreeView to facilitate handling of user 
editing of item text.

http://pr.stewartsplace.org.uk/d/sdwf/

Stewart.