Major header cleanup: removed redundant comments (single-line function/type...

Major header cleanup: removed redundant comments (single-line function/type descriptions are left for convenience), removed parse()/as_utf16(), removed deprecated function tests

git-svn-id: http://pugixml.googlecode.com/svn/trunk@746 99668b35-9821-0410-8761-19e4c4f06640