[CONNECT-263] Handle special characters in XML attributes.

Convert double quote to &quot; on autosave,
and convert &quot; to double quote when parsing XML attribute values.

coxml/document.c
Altered: "document_atb_value()" to unserialize xml string attribute value.

coxml/xmlparse.c
Replaced (unused) Mnemonichs with character literals to avoid text editor issues.
Added: "translate_string_with_string_impl()", "translate_string_with_string()", "translate_string_with_string_startpos()";
"fprintf_xml_string_attribute()"; "unserialize_xml_string_attribute_value()".

coxml/xmlparse.h
Added: "translate_string_with_string()", "translate_string_with_string_startpos()";
"fprintf_xml_string_attribute()"; "unserialize_xml_string_attribute_value()".

tools/strukt/occirest.c
Altered: "generate_occi_rest_builder()" to call "fprintf_xml_string_attribute()" when writing out xml attribute strings.