removed some warnings by casting xmlChar to unsigned int and a couple of

* DOCBparser.c HTMLparser.c entities.c parser.c relaxng.c
  xmlschemas.c xpath.c: removed some warnings by casting xmlChar
  to unsigned int and a couple of others.
* xmlschemastypes.c: fixes a segfault on empty hexBinary strings
Daniel
diff --git a/xmlschemastypes.c b/xmlschemastypes.c
index 006dd90..7bd8a6e 100644
--- a/xmlschemastypes.c
+++ b/xmlschemastypes.c
@@ -1924,6 +1924,8 @@
             unsigned long lo = 0, mi = 0, hi = 0;
 	    unsigned long *base;
 
+	    if (cur == NULL)
+	        goto return1;
             tmp = cur;
             while (((*tmp >= '0') && (*tmp <= '9')) ||
                    ((*tmp >= 'A') && (*tmp <= 'F')) ||