Patch for better diagnostics

[Tom Schindl]

When we pass an string with an length less than 4 to xs_get_styles_str 
we return undef which causes an error in the provider shown in this thread:

http://axkit.org/cgi-bin/ezmlm-cgi?3:mss:8455:200501:olieabalojlfdbdkfcoe
This patch only adds a carp-message because i have not searched until 
now if there are situations where an return of undef is desired although 
I don't think that's the case.

Tom
Index: AxKit.xs
===================================================================
RCS file: /home/cvspublic/xml-axkit/AxKit.xs,v
retrieving revision 1.7
diff -u -r1.7 AxKit.xs
--- AxKit.xs	31 Jan 2004 19:28:32 -0000	1.7
+++ AxKit.xs	18 Jan 2005 12:46:54 -0000
@@ -457,6 +457,7 @@
         xmlLoadExtDtdDefaultValue = 0;
         
         if (!ptr || len < 4) {
+	    carp("You have not passed in a valid XML-String: %s", ptr);
             XSRETURN_UNDEF;
         }