XPath stack optimization: Reduce convert_number_to_string stack usage by reducing mantissa_buffer size and filling resulting string on heap without an extra copy from stack.
XPath stack optimization: Reduce convert_number_to_string stack usage by reducing mantissa_buffer size and filling resulting string on heap without an extra copy from stack.

git-svn-id: febc13fe83507aab7d46ca3748413bb6c67ab8eb@933 99668b35-9821-0410-8761-19e4c4f06640

zeux/pugixml,zeux/pugixml,zeux/pugixml,zeux/pugixml