Bug #804 - URL link and break line

- Addressed bug #804 by allowing rc.hyphenate to control whether hyphens are
  inserted when long lines are broken.  This may help prevent xterm from
  mis-parsing URLs in task annotations, when wrapped (thanks to Yann Davin).
- Added unit tests.

src/commands/CmdShow.cpp

@@ -151,6 +151,7 @@ int CmdShow::execute (std::string& output)
     " extensions"
     " fontunderline"
     " gc"
+    " hyphenate"
     " import.synonym.bg"
     " import.synonym.description"
     " import.synonym.due"