Escape directive-like document content

Author: tompng

History.rdoc

@@ -163,7 +163,7 @@
   * Moved old DEVELOPERS file to CONTRIBUTING to match github conventions.
   * TomDoc output now has a "Returns" heading.  Issue #234 by Brian Henderson
   * Metaprogrammed methods can now use the :args: directive in addition to the
-    :call-seq: directive.  Issue #236 by Mike Moore.
+    \:call-seq: directive.  Issue #236 by Mike Moore.
   * Sections can be linked to using "@" like labels.  If a section and a label
     have the same name the section will be preferred.  Issue #233 by Brian
     Henderson.

doc/rdoc/markup_reference.rb

@@ -1245,7 +1245,7 @@ def dummy_instance_method(foo, bar); end;
   #
   # Here is the <tt>:call-seq:</tt> directive given for the method:
   #
-  #   :call-seq:
+  #   \:call-seq:
   #     call_seq_directive(foo, bar)
   #     Can be anything -> bar
   #     Also anything more -> baz or bat

lib/rdoc/parser/ruby.rb

@@ -120,7 +120,7 @@
 #   # :singleton-method: some_method!
 #
 # You can define arguments for metaprogrammed methods via either the
-# :call-seq:, :arg: or :args: directives.
+# \:call-seq:, :arg: or :args: directives.
 #
 # Additionally you can mark a method as an attribute by
 # using :attr:, :attr_reader:, :attr_writer: or :attr_accessor:.  Just like