Switch to using Halibut's new direct .CHM generation.

This allows me to remove HTML Help Workshop completely from my build
dependencies, and good riddance!

Buildscr

@@ -139,8 +139,7 @@ ifneq "$(MAKEARGS)" "" set Makeargs $(Makeargs) $(MAKEARGS)
 in putty do ./mksrcarc.sh
 in putty do ./mkunxarc.sh '$(Autoconfver)' '$(Uxarcsuffix)' $(Docmakever)
 in putty do perl mkfiles.pl
-in putty/doc do make $(Docmakever) putty.hlp
-in putty/doc do make $(Docmakever) chm
+in putty/doc do make $(Docmakever) putty.hlp putty.chm
 
 # Munge the installer script locally so that it reports the version
 # we're really building.
@@ -174,11 +173,6 @@ delegate windows
   # arguments and sign them all in place.
   ifneq "$(winsigncode)" "" in putty/windows do $(winsigncode) -i https://www.chiark.greenend.org.uk/~sgtatham/putty/ build*/*.exe
 
-  # Ignore exit code from hhc, in favour of seeing whether the .chm
-  # file was created. (Yuck; but hhc appears to return non-zero
-  # exit codes on whim.)
-  in putty/doc with htmlhelp do/win hhc putty.hhp & type putty.chm >nul
-
   # Build a WiX MSI installer, for each of build32 and build64.
   in putty/windows with wix do/win candle -arch x86 -dWin64=no -dBuilddir=build32\ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installer32.msi
   in putty/windows with wix do/win candle -arch x64 -dWin64=yes -dBuilddir=build64\ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installer64.msi
@@ -196,7 +190,6 @@ delegate windows
   return putty/windows/build32/*.map
   return putty/windows/build64/*.exe
   return putty/windows/build64/*.map
-  return putty/doc/putty.chm
   return putty/windows/installer32.msi
   return putty/windows/installer64.msi
   return putty/windows/Output/installer.exe

doc/Makefile

@@ -44,19 +44,17 @@ INPUTS = $(patsubst %,%.but,$(CHAPTERS))
 HALIBUT = halibut
 
 index.html: $(INPUTS)
-	$(HALIBUT) --text --html --winhelp $(INPUTS)
+	$(HALIBUT) --text --html --winhelp --chm $(INPUTS)
 
-# During formal builds it's useful to be able to build this one alone.
+# During formal builds it's useful to be able to build these ones alone.
 putty.hlp: $(INPUTS)
 	$(HALIBUT) --winhelp $(INPUTS)
+putty.chm: $(INPUTS)
+	$(HALIBUT) --chm $(INPUTS)
 
 putty.info: $(INPUTS)
 	$(HALIBUT) --info $(INPUTS)
 
-chm: putty.hhp
-putty.hhp: $(INPUTS) chm.but
-	$(HALIBUT) --html $(INPUTS) chm.but
-
 MKMAN = $(HALIBUT) --man=$@ mancfg.but $<
 MANPAGES = putty.1 puttygen.1 plink.1 pscp.1 psftp.1 puttytel.1 pterm.1 \
            pageant.1

doc/blurb.but

@@ -14,10 +14,16 @@ page</a>.</p>}
 
 \cfg{info-max-file-size}{0}
 
+\cfg{chm-contents-filename}{index.html}
+\cfg{chm-template-filename}{%k.html}
+\cfg{chm-head-end}{<link rel="stylesheet" type="text/css" href="chm.css">}
+\cfg{chm-extra-file}{chm.css}
+
 \cfg{xhtml-contents-filename}{index.html}
 \cfg{text-filename}{puttydoc.txt}
 \cfg{winhelp-filename}{putty.hlp}
 \cfg{info-filename}{putty.info}
+\cfg{chm-filename}{putty.chm}
 
 PuTTY is a free (MIT-licensed) Windows Telnet and SSH client. This
 manual documents PuTTY, and its companion utilities PSCP, PSFTP,