+ - Run Halibut to build the docs. Define VERSION on the make command
+ line to override the version strings, since Subversion revision
+ numbers are less meaningful on a tag.
+ + change into the doc subdir
+ + run `make VERSION="PuTTY release 0.XX" chm', then run `hhc
+ putty.hhp' to build the .CHM
+ + then run `make mostlyclean' (destroys the hhc input files but
+ _not_ the .CHM)
+ + then `make VERSION="PuTTY release 0.XX"'