Big fixes of pattern compilations

The problem is that "@node()", "attribute::node()", "child::node()" and
"node()" are all handled in different code paths and only the latter
works.

Then, I noticed that the handling of match="child::name" is wrong. It
matches the parents of <name> elements although it should be treated
exactly like match="name". So the whole XSLT_OP_CHILD stuff is
unneeded.

I also found that xsltScanName behaves a bit strange with regard to
':' characters. It doesn't parse an XML Name like the documentation
says. It's better to use xsltScanNCName instead.

Another minor issue is that the parser currently allows invalid
expressions like match="element*" because of lines 1745-1747 in
pattern.c in trunk.

* libxslt/pattern.c: fix all those problems
* tests/REC/Makefile.am tests/REC/test-5.2-19* tests/REC/test-5.2-20*
  tests/REC/test-5.2-21*: add test cases to the regression suite