Move site type specific linkification tests to appropriate place.

src/Linkification/Linkify.coffee

@@ -14,7 +14,7 @@ Linkify =
   node: ->
     return Embedding.events @ if @isClone
     return unless Linkify.regString.test @info.comment
-    for link in $$ 'a', @nodes.comment when ImageHost.test(link.hostname) or /\bnofollow\b/.test(link.rel)
+    for link in $$ 'a', @nodes.comment when g.SITE.isLinkified?(link)
       $.addClass link, 'linkify'
       ImageHost.fixLinks [link] if ImageHost.useFaster
       Embedding.process link, @

src/site/SW.tinyboard.coffee

@@ -166,3 +166,6 @@ SW.tinyboard =
   isThumbExpanded: (file) ->
     # Detect old Tinyboard image expansion that changes src attribute on thumbnail.
     $.hasClass file.thumb.parentNode, 'expanded'
+
+  isLinkified: (link) ->
+    /\bnofollow\b/.test(link.rel)

src/site/SW.yotsuba.coffee

@@ -168,3 +168,6 @@ SW.yotsuba =
     while i < 8
       msg = (msg << 5) - msg + uid.charCodeAt i++
     (msg >> 8) & 0xFFFFFF
+
+  isLinkified: (link) ->
+    ImageHost.test(link.hostname)