Promoted _auxtype to a struct to gain access to additional fields

While creating files there was no possibility to explicitly set the
time or date.
This is necessary for example while copying files since the original
time and date should be kept.

include/apple2.h

@@ -139,7 +139,12 @@ extern unsigned char _dos_type;
  * following variables to determine the file type and the aux type to use.
  */
 extern unsigned char _filetype;  /* Default 6 */
-extern unsigned int  _auxtype;   /* Default 0 */
+extern struct {
+    unsigned int aux;
+    unsigned char storage;
+    unsigned int date;
+    unsigned int time;
+} _auxtype;   /* Default 0 */
 
 /* The addresses of the static drivers */
 #if !defined(__APPLE2ENH__)