fixed the validation of sequences content model when some of the blocks

* xmlregexp.c xmlschemas.c: fixed the validation of sequences
  content model when some of the blocks have min or max, and a couple
  of bugs found in the process.
* result/schemas/list0* test/schemas/list0*: added some specific
  regression tests
Daniel
diff --git a/result/schemas/choice_2_1 b/result/schemas/choice_2_1
index e69de29..e4338de 100644
--- a/result/schemas/choice_2_1
+++ b/result/schemas/choice_2_1
@@ -0,0 +1 @@
+./test/schemas/choice_1.xml validates