doc: disable smart typography (eg en-dash) in MANUAL.* and man page

Before this change MANUAL.html and rclone.1 would show flags like –addr

Now it shows --addr which is easy to copy and paste.

This was pointed out in rclone#4362

Makefile

@@ -109,16 +109,16 @@ tidy:
 doc:	rclone.1 MANUAL.html MANUAL.txt rcdocs commanddocs
 
 rclone.1:	MANUAL.md
-	pandoc -s --from markdown --to man MANUAL.md -o rclone.1
+	pandoc -s --from markdown-smart --to man MANUAL.md -o rclone.1
 
 MANUAL.md:	bin/make_manual.py docs/content/*.md commanddocs backenddocs
 	./bin/make_manual.py
 
 MANUAL.html:	MANUAL.md
-	pandoc -s --from markdown --to html MANUAL.md -o MANUAL.html
+	pandoc -s --from markdown-smart --to html MANUAL.md -o MANUAL.html
 
 MANUAL.txt:	MANUAL.md
-	pandoc -s --from markdown --to plain MANUAL.md -o MANUAL.txt
+	pandoc -s --from markdown-smart --to plain MANUAL.md -o MANUAL.txt
 
 commanddocs: rclone
 	XDG_CACHE_HOME="" XDG_CONFIG_HOME="" HOME="\$$HOME" USER="\$$USER" rclone gendocs docs/content/