spread some serious anti bitrot all over the place:
- parserInternals.c parserInternals.h parser.c Makefile.am:
  created a new module parserInternals.c, moved most of the
  code shared by the various parsers there, as well as
  deprecated  code from parser.c. More cleanup of parser.c
- uri.c: fixed a problem when URI is NULL
- valid.c: speedup when looking for an attribute declaration
Daniel