adding "make valgrind" running the full regression tests (except python * Makefile.am: adding "make valgrind" running the full regression tests (except python ones) under Valgrind (using valgrind -q which was kindly added by the author). * valid.c: stupid bug pinpointed by Valgrind, the regression tests passes cleanly now except an obcure floating point initialization raised in log10() in one XPath regression test ??? * tree.c: edited some comments to close #75244 Daniel