fixing bug #104081 with xs:all with an element holding minOccurs="0" added

* xmlschemas.c: fixing bug #104081 with xs:all with an element
  holding minOccurs="0"
* test/schemas/all_* result/schemas/all_*: added some regression
  tests for that bug
* xmllint.c xmlreader.c: patches from Joerg Schmitz-Linneweber and
  Garry Pennington to compile without schemas support.
Daniel
diff --git a/result/schemas/all_2_3 b/result/schemas/all_2_3
new file mode 100644
index 0000000..8186e82
--- /dev/null
+++ b/result/schemas/all_2_3
@@ -0,0 +1 @@
+./test/schemas/all_3.xml validates