Added features that allow the reader to accept common non-standard JSON.

This is a version of patch #17, from Clay Wood:

    http://sourceforge.net/p/jsoncpp/patches/17/

git-svn-id: https://svn.code.sf.net/p/jsoncpp/code/trunk/jsoncpp@280 1f120ed1-78a5-a849-adca-83f0a9e25bb6