bug#7848: 23.2.91; Can't build with MinGW

[Stefan Monnier]

> Sorry.  Please try replacing this:

>   SET_SYMBOL_VAL (XSYMBOL (Qlibpng_version), make_number (PNG_LIBPNG_VER));
[...]
>   XSYMBOL (Qlibpng_version)->value = make_number (PNG_LIBPNG_VER);

I would recommend to stay away from such low-level code unless you're
writing code that tries to implement part of the binding-semantics
of Emacs.  I.e. just use Fset.


        Stefan