applied DSO support patch 2 from Joel Reed Daniel

* Makefile.am config.h.in configure.in error.c libxml-2.0.pc.in
  testModule.c testdso.c xml2-config.in xmllint.c xmlmodule.c
  include/libxml/Makefile.am include/libxml/xmlerror.h
  include/libxml/xmlmodule.h include/libxml/xmlversion.h.in
  include/libxml/xmlwin32version.h.in: applied DSO support
  patch 2 from Joel Reed
Daniel

testModule.c

@@ -0,0 +1,60 @@
+/*
+ * testModule.c : a small tester program for xmlModule
+ *
+ * See Copyright for the status of this software.
+ *
+ * joelwreed@comcast.net
+ */
+
+#include "libxml.h"
+#ifdef LIBXML_MODULES_ENABLED
+#include <libxml/xmlversion.h>
+
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+
+#include <libxml/xmlmemory.h>
+#include <libxml/debugXML.h>
+#include <libxml/xmlmodule.h>
+
+#ifdef _WIN32
+#define MODULE_PATH "."
+#include <stdlib.h> /* for _MAX_PATH */
+#define PATH_MAX _MAX_PATH
+#else
+#define MODULE_PATH ".libs"
+#endif
+
+typedef int (*hello_world_t)();
+ 
+int main(int argc ATTRIBUTE_UNUSED, char **argv ATTRIBUTE_UNUSED) {
+    xmlChar filename[PATH_MAX];
+    xmlModulePtr module = NULL;
+    hello_world_t hello_world = NULL;
+
+    /* build the module filename, and confirm the module exists */
+    xmlStrPrintf(filename, sizeof(filename), "%s/testdso%s", (const xmlChar*)MODULE_PATH, (const xmlChar*)LIBXML_MODULE_EXTENSION);
+
+    module = xmlModuleOpen((const char*)filename);
+    if (module)
+      {
+        hello_world = (hello_world_t)xmlModuleSymbol(module, "hello_world");
+        (*hello_world)();
+
+        xmlModuleClose(module);
+      }
+
+    xmlMemoryDump();
+
+    return(0);
+}
+
+#else
+#include <stdio.h>
+int main(int argc ATTRIBUTE_UNUSED, char **argv ATTRIBUTE_UNUSED) {
+    printf("%s : Module support not compiled in\n", argv[0]);
+    return(0);
+}
+#endif /* LIBXML_SCHEMAS_ENABLED */