Changes in Mini-XML 1.1.1

• The private mxml_add_ch() function did not update the start-of-buffer pointer which could cause a crash when using mxmlSaveString().
• The private mxml_write_ws() function called putc() instead of using the proper callback which could cause a crash when using mxmlSaveString().
• Added a mxmlSaveAllocString() convenience function for saving an XML node tree to an allocated string.