md: add backtick support (port)

This takes md.jsf from JOE 4.4 and applies 6b2a3be746 ontop.

README.md

@@ -31,6 +31,7 @@ Files with contributions (or unclear license info):
 * [ini.jsf](https://github.com/cmur2/joe-syntax/blob/master/ini.jsf) which is created by [Christian Nicolai](https://github.com/cmur2) with contributions from [Todd Lewis](https://github.com/utoddl)
 * [json.jsf](https://github.com/cmur2/joe-syntax/blob/master/json.jsf) which is entirely contributed by [Rebecca Turner](https://github.com/iarna) under GPL v2 or any later version and compatible ISC license ([comment](https://github.com/cmur2/joe-syntax/pull/14#issuecomment-78058037))
 * [lsl.jsf](https://github.com/cmur2/joe-syntax/blob/master/lsl.jsf) which is from [Zai Lynch](https://wiki.secondlife.com/wiki/User:Zai_Lynch) under GPL v1 (delivered by [Rebecca Turner](https://github.com/iarna))
+* [md.jsf](https://github.com/cmur2/joe-syntax/blob/master/md.jsf) which is created by [Christian Nicolai](https://github.com/cmur2) and then modified by Jonas Rosling and [Todd Lewis](https://github.com/utoddl)
 * [sql.jsf](https://github.com/cmur2/joe-syntax/blob/master/sql.jsf) which is from an "unknown source" (delivered by [Rebecca Turner](https://github.com/iarna))
 * [yaml.jsf](https://github.com/cmur2/joe-syntax/blob/master/yaml.jsf) which is created by [Christian Nicolai](https://github.com/cmur2) with bug fixes from [Todd Lewis](https://github.com/utoddl)
 

md.jsf

@@ -0,0 +1,153 @@
+# JOE syntax highlight file for Markdown
+# by Christian Nicolai (http://mycrobase.de)
+
+# And yes, this *is* a joke :p
+
+# bold parsing is not that perfect since this works: **bold__
+
+=Idle
+=Tag		green
+=Escape		bold
+=Bad		bold red
+
+=Bold		bold
+=Headline	bold yellow
+=Quote		green
+=Code		green
+=List		yellow
+=LinkDesc	green
+=Link		blue
+=Rule		inverse
+
+:line_start Idle
+	*		idle		noeat
+	"#"		headline_prefix recolor=-1
+	">"		quote		recolor=-1
+	" "		maybe_code1
+	"\t"		code
+	"-*"		maybe_list
+
+:idle Idle
+	*		idle
+	"\n"		line_start
+	"<"		tag		recolor=-1
+	"\\"		escape		recolor=-1
+	"*_"		maybe_bold1
+	"["		maybe_link_desc1
+	"`"		backtick	buffer noeat
+
+:headline_prefix Idle
+	*		headline
+	"#"		headline_prefix
+
+:headline Headline
+	*		headline
+	"\n"		line_start
+
+:quote Quote
+	*		quote
+	"\n"		line_start
+
+:maybe_code1 Idle
+	*		idle
+	" "		maybe_code2
+
+:maybe_code2 Idle
+	*		idle
+	" "		maybe_code3
+
+:maybe_code3 Idle
+	*		idle
+	" "		code		recolor=-4
+
+:code Code
+	*		code
+	"\n"		line_start
+
+:maybe_list Idle
+	*		idle
+	" "		list
+	"-*"		maybe_rule1
+
+:list List
+	*		list
+	"\n"		line_start
+
+:maybe_rule1 Idle
+	*		idle
+	"-*"		rule		recolor=-3
+
+:rule Rule
+	*		rule
+	"\n"		line_start
+
+:tag Tag
+	*		idle
+	"a-z0-9 /"	tag
+	">"		idle
+
+# do escaping of *_ and so on
+:escape Escape
+	*		idle
+
+:maybe_bold1 Idle
+	*		idle		noeat
+	"*_"		bold		recolor=-2
+
+:bold Bold
+	*		bold
+	"\n"		line_start	# end if we reach newline during bold
+	"*_"		maybe_end_bold
+
+:maybe_end_bold Bold
+	*		bold
+	"*_"		end_bold
+
+:end_bold Bold
+	*		idle		noeat
+
+:maybe_link_desc1 Idle
+	*		maybe_link_desc	mark
+
+:maybe_link_desc Idle
+	*		maybe_link_desc
+	"]"		maybe_end_link_desc	markend
+
+:maybe_end_link_desc Idle
+	*		idle
+	"("		link_inline1	recolormark
+	"["		link_ref1	recolormark
+
+:link_inline1 LinkDesc
+	*		link_inline	noeat
+
+:link_inline Link
+	*		link_inline
+	")"		link_end	noeat
+
+:link_ref1 LinkDesc
+	*		link_ref	noeat
+
+:link_ref Link
+	*		link_ref
+	"]"		link_end	noeat
+
+:link_end Idle
+	*		idle
+
+:backtick Quote
+	*		backtick_body	save_s noeat
+	"`"		backtick
+
+:backtick_body Code
+	*		backtick_body
+	"`"             backtick_end_maybe	buffer
+
+:backtick_end_maybe Code
+	*		backtick_body	strings
+	"&"		backtick_end
+done
+	"`"		backtick_end_maybe
+
+:backtick_end Quote
+	*		idle		noeat