added the routine xmlNanoHTTPContentLength to the external API

* nanohttp.c, include/libxml/nanohttp.h: added the routine
  xmlNanoHTTPContentLength to the external API (bug151968).
* parser.c: fixed unnecessary internal error message (bug152060);
  also changed call to strncmp over to xmlStrncmp.
* encoding.c: fixed compilation warning (bug152307).
* tree.c: fixed segfault in xmlCopyPropList (bug152368); fixed
  a couple of compilation warnings.
* HTMLtree.c, debugXML.c, xmlmemory.c: fixed a few compilation
  warnings; no change to logic.
10 files changed