Remove remaining MSDOS support code

The remaining DOS source files where already removed in
26a0a24f38. This removes the remaining __DOS__
and __DJGPP__ (the DOS gcc) code paths.

Closes https://github.com/wxWidgets/wxWidgets/pull/100

src/common/time.cpp

@@ -71,7 +71,7 @@
     #include <sys/timeb.h>
 #endif
 
-#if defined(__DJGPP__) || defined(__WINE__)
+#if defined(__WINE__)
     #include <sys/timeb.h>
     #include <values.h>
 #endif
@@ -172,7 +172,7 @@ int wxGetTimeZone()
             gmtoffset += 3600;
     }
     return (int)gmtoffset;
-#elif defined(__DJGPP__) || defined(__WINE__)
+#elif defined(__WINE__)
     struct timeb tb;
     ftime(&tb);
     return tb.timezone*60;