- parser.c xmlIO.[ch]: fixed the problem of encoding support

when using in memory parsing. Need some cleanup.
- xmllint.c configure.in: added a --memory flag to test memory
  parsing
Daniel

xmlIO.c

@@ -89,6 +89,11 @@ int xmlOutputCallbackInitialized = 0;
  *									*
  ************************************************************************/
 
+int
+xmlNop(void) {
+    return(0);
+}
+
 /**
  * xmlFdMatch:
  * @filename:  the URI for matching
@@ -1044,6 +1049,35 @@ xmlParserInputBufferCreateFd(int fd, xmlCharEncoding enc) {
     return(ret);
 }
 
+/**
+ * xmlParserInputBufferCreateMem:
+ * @mem:  the memory input
+ * @size:  the length of the memory block
+ * @enc:  the charset encoding if known
+ *
+ * Create a buffered parser input for the progressive parsing for the input
+ * from a file descriptor
+ *
+ * Returns the new parser input or NULL
+ */
+xmlParserInputBufferPtr
+xmlParserInputBufferCreateMem(const char *mem, int size, xmlCharEncoding enc) {
+    xmlParserInputBufferPtr ret;
+
+    if (size <= 0) return(NULL);
+    if (mem == NULL) return(NULL);
+
+    ret = xmlAllocParserInputBuffer(enc);
+    if (ret != NULL) {
+        ret->context = (void *) mem;
+	ret->readcallback = (xmlInputReadCallback) xmlNop;
+	ret->closecallback = NULL;
+	xmlBufferAdd(ret->buffer, (const xmlChar *) mem, size);
+    }
+
+    return(ret);
+}
+
 /**
  * xmlOutputBufferCreateFd:
  * @fd:  a file descriptor number