Windows: product names, the editors, WSL; the Linux page's image step

Assembled from development commit c3c40f6c8fca. Since 830b193: on Windows the
products carry Windows names (ktext.exe, klammertext.dll, document.dll,
reflect.dll) and the console's output code page is UTF-8 for a run; the
editor tooling works on Windows (VS Code, Sublime Text, Vim, with the
interpreter's name chosen by platform) and Notepad++ joins it
(doc/edit/notepadpp: a User Defined Language and two Run-menu commands);
a sixth install page, doc/install/windows_wsl_install.md, for Linux
inside WSL; the Windows page opens with the three routes and gains its
editor section, the PowerShell quoting and Path notes; the Linux page
installs OpenImageIO from the python3-openimageio package and verifies
with kdiag --machine; the README lists all six install pages. Linux and
macOS behaviour is unchanged.

ref/Makefile

@@ -4,7 +4,8 @@
 # character tables and return Klammertext (a "@table" call and such), which
 # the .kt fragments in this directory then render for whichever target is
 # in force.  They are reached through "@eval :cpp", so this builds a DSO
-# loaded at run time, not part of libklammertext.so.
+# loaded at run time, not part of the shared library: reflect.so, on
+# Windows reflect.dll (makefile.env's DSO).
 #
 # Adapted from sks/document/Makefile.  Two things differ and both matter:
 # ref/ has no sks dependencies (a generator returns Klammertext, so it
@@ -19,10 +20,11 @@ include $(K)/env/makefile.env
 # reflect.cpp includes (machine, character, error, show).  No local -I.
 
 LIBDIR := $(K)/lib
-LIBRARY := $(LIBDIR)/libklammertext.so
+LIBRARY := $(LIBDIR)/$(KLAMMERTEXT_LIBFILE)
+REFLECT := reflect$(DSO)
 
-# "../lib", not "../../lib": reflect.so sits in $(K)/ref, so one level up
-# reaches $(K)/lib.  (sks/document.so needs two, which is what this was
+# "../lib", not "../../lib": the DSO sits in $(K)/ref, so one level up
+# reaches $(K)/lib.  (sks/document's needs two, which is what this was
 # copied from -- a wrong rpath here shows up only at dlopen time, and only
 # where the loading process does not already have the library.)
 REF_LDFLAGS := $(SHARED) $(EXPORT_DYNAMIC) -Wl,-rpath,'$(ORIGIN)/../lib' -L$(LIBDIR)
@@ -34,7 +36,7 @@ DEPFLAGS = -MMD -MP -MF $(@:.o=.d)
 
 .PHONY: all clean
 
-all : reflect.so
+all : $(REFLECT)
 
 %.o : %.cpp
 	@echo Compiling $<
@@ -46,11 +48,11 @@ all : reflect.so
 # for the same file -- compiling reflect.cpp inline AND linking reflect.o --
 # defines every symbol in it twice.  Building through the pattern rule also
 # gets reflect.d, so a header change rebuilds it.
-reflect.so : $(OBJECTS) $(LIBRARY)
+$(REFLECT) : $(OBJECTS) $(LIBRARY)
 	$(CXX) $(CPPFLAGS) $(CXXFLAGS) $(REF_LDFLAGS) $(LDFLAGS) \
 		-o $@ $(OBJECTS) $(KLAMMERTEXT_LIB) $(LDLIBS)
 
 clean :
-	rm -f $(OBJECTS) $(DEPFILES) *.so *~
+	rm -f $(OBJECTS) $(DEPFILES) *.so *.dll *~
 
 -include $(DEPFILES)