Rewriting OctalUnescaper as a hand rolled parser (all of 4 characters), instead of trying to handle the conversion via repeated attempts to convert the numbers. This fixes bugs, see LANG-929, and also changes the behaviour for 'illegal' octals such as \999. Instead of throwing NumberFormatException, it will now ignore them. This seems the better behaviour. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1535914 13f79535-47bb-0310-9956-ffa450edef68