applied patch from Andrew W. Nosenko to expose if zlib support was

* configure.in parser.c xmllint.c include/libxml/parser.h
  include/libxml/xmlversion.h.in: applied patch from Andrew W. Nosenko
  to expose if zlib support was compiled in, in the header, in the
  feature API and in the xmllint --version output.
Daniel
diff --git a/parser.c b/parser.c
index a426b79..ceb91d2 100644
--- a/parser.c
+++ b/parser.c
@@ -807,6 +807,12 @@
 #else
             return(0);
 #endif 
+        case XML_WITH_ZLIB:
+#ifdef LIBXML_ZLIB_ENABLED
+            return(1);
+#else
+            return(0);
+#endif
         default:
 	    break;
      }