#3 Macros from xpath.h not included

[Thomas Kaltenbrunner]

The release 2.6.19 does not contain the functions that
replace the macros from xpath.h.
An older version defined them in the implementation
part of libxml2.pas.
Since the files are generated automatically, the
"macro-functions" should be defined in a seperate unit.

Grьяe
Thomas Jдckel