[DOXIA-386] Snippet Macro: Reference file does not support UTF-8 file format to generate the page garbage

- Added macro parameter 'encoding' which takes in specific encoding

git-svn-id: https://svn.apache.org/repos/asf/maven/doxia/doxia/trunk@1543585 13f79535-47bb-0310-9956-ffa450edef68