We should certainly have a Formula::share()

I removed this months back as I found it confusing, does it mean:

prefix+'share' or prefix+'share'+name()

But honestly, it's obvious, it's the former. It's the same as the other path
functions.

Library/Homebrew/formula.rb

@@ -91,6 +91,7 @@ class Formula
   def man1; man+'man1' end
   def info; prefix+'share'+'info' end
   def include; prefix+'include' end
+  def share; prefix+'share' end
 
   # reimplement if we don't autodetect the download strategy you require
   def download_strategy