Enhanced xmlXPathRunStreamEval, fixed handling of depth/level for cases

* xpath.c, pattern.c: Enhanced xmlXPathRunStreamEval, fixed
  handling of depth/level for cases like union operator
  (bug #306348 reported by Bob Stayton).  Also enhanced
  several comments throughout pattern.c.
* doc/apibuild.py: fixed problem in handling of
  'signed' declaration.  Rebuilt the docs.
diff --git a/doc/apibuild.py b/doc/apibuild.py
index 518c93c..5686238 100755
--- a/doc/apibuild.py
+++ b/doc/apibuild.py
@@ -1201,7 +1201,9 @@
 	    return token
 
 	while token[0] == "name" and ( 
-	      token[1] == "const" or token[1] == "unsigned"):
+	      token[1] == "const" or \
+	      token[1] == "unsigned" or \
+	      token[1] == "signed"):
 	    if self.type == "":
 	        self.type = token[1]
 	    else: