fixed xmlHasNsProp() bugs for defaulted from DTD attribs, added a specific

* tree.c python/tests/Makefile.am python/tests/attribs.py:
  fixed xmlHasNsProp() bugs for defaulted from DTD attribs,
  added a specific regression test
* python/generator.py: xmlHasNsProp() and xmlHasProp() shall
  not raise exceptions when failing to find the attribute.
Daniel

python/tests/attribs.py

@@ -0,0 +1,34 @@
+#!/usr/bin/python -u
+import sys
+import libxml2
+
+# Memory debug specific
+libxml2.debugMemory(1)
+
+#
+# Testing XML document serialization
+#
+doc = libxml2.parseDoc(
+"""<?xml version="1.0" encoding="iso-8859-1"?>
+<!DOCTYPE test [
+<!ELEMENT test (#PCDATA) >
+<!ATTLIST test xmlns:abc CDATA #FIXED "http://abc.org" >
+<!ATTLIST test abc:attr CDATA #FIXED "def" >
+]>
+<test />
+""")
+elem = doc.getRootElement()
+attr = elem.hasNsProp('attr', 'http://abc.org')
+if attr == None or attr.serialize()[:-1] != """<!ATTLIST test abc:attr CDATA #FIXED "def">""":
+    print "Failed to find defaulted attribute abc:attr"
+    sys.exit(1)
+
+doc.freeDoc()
+
+# Memory debug specific
+libxml2.cleanupParser()
+if libxml2.debugMemory(1) == 0:
+    print "OK"
+else:
+    print "Memory leak %d bytes" % (libxml2.debugMemory(1))
+    libxml2.dumpMemory()