Fix: Core: Implement true escaping for the five predefined XML entities

See:
http://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references#Predefined_entities_in_XML

Name	Character Unicode (decimal)	Standard Description
quot	"	  U+0022 (34)		XML 1.0	 double quotation mark
amp	&	  U+0026 (38)		XML 1.0	 ampersand
apos	'	  U+0027 (39)		XML 1.0	 apostrophe (= apostrophe-quote)
lt	<	  U+003C (60)		XML 1.0	 less-than sign
gt	>	  U+003E (62)		XML 1.0	 greater-than sign
Doc: Clusters_from_Scratch: Fix pacemaker version