File "rules" has instructional text as comments near top.

2) Convert all text files in repo to LF line ending form.
   Any checkout done with "rules" in play will convert the working
   tree to native line ending, while keeping repo as LF line ending.

Add include/dialog_shim.h and common/dialog_shim.cpp for use by wxformbuilder's "subclass a wxDialog" support.
This works, but in my version of wxformbuilder there is a bug which does not properly show the 
subclass property, even though it is still in play.  This happens after saving then loading the *.fbp file.
So it is a nuisance bug, but does not affect functionality.