[AD] _al_file_size removal

[Peter Wang <tjaden@xxxxxxxxxx>]

Hi, the renaming of _al_file_size to _al_file_file_ex causes an exported
symbol to disappear:

    % ./misc/fixdll.sh
    Scanning for API symbols...
    Scanning for WinAPI symbols...
    Scanning for internal symbols...
    Checking against existing symbol list...
     *** Error !!! ***
      symbols missing => DLL binary compatibility broken
      you need to add the following symbols:
	_al_file_size

As far as I can tell, we can restore it by defining

    long _al_file_size(AL_CONST char *filename)
    {
       return (long)_al_file_size_ex(filename);
    }

in file.c, or even

    long _al_file_size(AL_CONST char *filename)
    {
       abort();
    }

since `_al_file_size' should not be used directly outside the library.
Can someone on Windows try this out and make sure a program compiled
with 4.2.0 works with 4.2 SVN?

Peter