* Added several type casts to increase C++ compatibility.

 * Added several type casts to increase C++ compatibility.
 * __fixargs__ is now an actual function symbol and no longer handled in the
   scanner.
 * Additional symbol __argsize__ that is a constant in normal functions and
   a const local variable for variadic functions. Using this symbol, the
   va_arg macro gets a lot simpler and smaller.
 * Added special code to handle the fixed parameters of a variadic function.
   The code has some overhead, but the va_fix macro is no longer needed (and
   the compiler generated code is better than va_fix anyway).

git-svn-id: svn://svn.cc65.org/cc65/trunk@652 b7a2c559-68d2-44c3-8de9-860c34a00d81