added two new macros IS_ASCII_LETTER and IS_ASCII_DIGIT used with (html)

* include/libxml/parserInternals.h: added two new macros
  IS_ASCII_LETTER and IS_ASCII_DIGIT used with (html)
  parsing and xpath for testing data not necessarily
  unicode.
* HTMLparser.c, xpath.c: changed use of IS_LETTER_CH and
  IS_DIGIT_CH macros to ascii versions (bug 153936).
4 files changed