build: get base of windows build for openzap going again (OPENZAP-55)

git-svn-id: http://svn.openzap.org/svn/openzap/trunk@682 a93c3328-9c30-0410-af19-c9cd2b2d52af

libs/openzap/src/zap_buffer.c

@@ -164,7 +164,7 @@ zap_size_t zap_buffer_read_loop(zap_buffer_t *buffer, void *data, zap_size_t dat
 		}
 		buffer->head = buffer->data;
 		buffer->used = buffer->actually_used;
-		len = zap_buffer_read(buffer, data + len, datalen - len);
+		len = zap_buffer_read(buffer, (char*)data + len, datalen - len);
 		buffer->loops--;
 	}
 	return len;