doc: add SSHFS Port Case Study document

doc/Makefile

@@ -1,4 +1,8 @@
-web: web/winfsp-design.html web/service-architecture.html web/winfsp.h.html
+web: \
+	web/winfsp-design.html \
+	web/service-architecture.html \
+	web/sshfs-port-case-study.html \
+	web/winfsp.h.html
 
 web/winfsp-design.html:
 	mkdir -p web
@@ -8,6 +12,10 @@ web/service-architecture.html:
 	mkdir -p web
 	asciidoc -b html4 -a hr= -s -o $@ service-architecture.adoc
 
+web/sshfs-port-case-study.html:
+	mkdir -p web
+	asciidoc -b html4 -a hr= -s -o $@ sshfs-port-case-study.adoc
+
 web/winfsp.h.html:
 	mkdir -p web
 	prettydoc -H-O -o web ../inc/winfsp/winfsp.h