changes for the 'usual' setup.py to allow building a libxml2-python module

* python/generator.py python/libxslt.c: changes for the 'usual'
  setup.py to allow building a libxml2-python
  module based on the same code. The initialization is however
  different the 2 .so files fo libxml2 and libxslt are identical and
  they entry point initialize both libraries. this is done to avoid
  some possible nasty problem since the Python don't merge the maps
  of all shared modules.
* python/libxsl.py: attempt to cope with the shared library loading
  problem when both modules are not merged.
Daniel

python/libxsl.py

@@ -1,6 +1,48 @@
-import libxml2mod
-import libxsltmod
-import libxml2
+#
+# Both libxml2mod and libxsltmod have a dependancy on libxml2.so
+# and they should share the same module, try to convince the python
+# loader to work in that mode if feasible
+#
+import sys
+try:
+    from dl import RTLD_GLOBAL, RTLD_NOW
+except ImportError:
+    RTLD_GLOBAL = -1
+    RTLD_NOW = -1
+    try:
+        import os
+	osname = os.uname()[0]
+	if osname == 'Linux':
+	    RTLD_GLOBAL = 0x00100
+	    RTLD_NOW = 0x00002
+	#
+	# is there a better method ?
+	#
+	else:
+	    print "libxslt could not guess RTLD_GLOBAL and RTLD_NOW " + \
+	          "on this platform: %s" % (osname)
+    except:
+	print "libxslt could not guess RTLD_GLOBAL and RTLD_NOW " + \
+	      "on this platform: %s" % (osname)
+
+if RTLD_GLOBAL != -1 and RTLD_NOW != -1:
+    try:
+	flags = sys.getdlopenflags() 
+	sys.setdlopenflags(RTLD_GLOBAL | RTLD_NOW)
+	try:
+	    import libxml2mod
+	    import libxsltmod
+	    import libxml2
+	finally:
+	    sys.setdlopenflags(flags)
+    except:
+	import libxml2mod
+	import libxsltmod
+	import libxml2
+else:
+    import libxml2mod
+    import libxsltmod
+    import libxml2
 
 #
 # Everything below this point is automatically generated