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

include/wx/defs.h

@@ -1130,8 +1130,7 @@ typedef wxUint32 wxDword;
     #define wxLongLongFmtSpec "I64"
 #elif (defined(SIZEOF_LONG_LONG) && SIZEOF_LONG_LONG >= 8)  || \
         defined(__GNUC__) || \
-        defined(__CYGWIN__) || \
-        (defined(__DJGPP__) && __DJGPP__ >= 2)
+        defined(__CYGWIN__)
     #define wxLongLong_t long long
     #define wxLongLongSuffix ll
     #define wxLongLongFmtSpec "ll"

include/wx/filefn.h

@@ -32,13 +32,6 @@
 #endif // __WINDOWS__
 #endif // native Win compiler
 
-#if defined(__DOS__)
-    #ifdef __DJGPP__
-        #include <io.h>
-        #include <unistd.h>
-    #endif
-#endif
-
 #ifdef __BORLANDC__ // Please someone tell me which version of Borland needs
                     // this (3.1 I believe) and how to test for it.
                     // If this works for Borland 4.0 as well, then no worries.

include/wx/filename.h

@@ -28,7 +28,7 @@ class WXDLLIMPEXP_FWD_BASE wxFFile;
 
 // this symbol is defined for the platforms where file systems use volumes in
 // paths
-#if defined(__WINDOWS__) || defined(__DOS__)
+#if defined(__WINDOWS__)
     #define wxHAS_FILESYSTEM_VOLUMES
 #endif
 

include/wx/math.h

@@ -75,7 +75,7 @@
     wxDECL_FOR_STRICT_MINGW32(int, _finite, (double))
 
     #define wxFinite(x) _finite(x)
-#elif ( defined(__GNUG__)||defined(__GNUWIN32__)||defined(__DJGPP__)|| \
+#elif ( defined(__GNUG__)||defined(__GNUWIN32__)|| \
       defined(__SGI_CC__)||defined(__SUNCC__)||defined(__XLC__)|| \
       defined(__HPUX__) ) && ( !defined(wxOSX_USE_IPHONE) || wxOSX_USE_IPHONE == 0 )
 #ifdef __SOLARIS__
@@ -89,7 +89,7 @@
 
 #if defined(__VISUALC__)||defined(__BORLAND__)
     #define wxIsNaN(x) _isnan(x)
-#elif defined(__GNUG__)||defined(__GNUWIN32__)||defined(__DJGPP__)|| \
+#elif defined(__GNUG__)||defined(__GNUWIN32__)|| \
       defined(__SGI_CC__)||defined(__SUNCC__)||defined(__XLC__)|| \
       defined(__HPUX__)
     #define wxIsNaN(x) isnan(x)

include/wx/platform.h

@@ -237,21 +237,6 @@
 #   define wxCOMPILER_BROKEN_CONCAT_OPER
 #endif /* __BORLANDC__ */
 
-/*
-   OS: first of all, test for MS-DOS platform. We must do this before testing
-       for Unix, because DJGPP compiler defines __unix__ under MS-DOS
- */
-#if defined(__GO32__) || defined(__DJGPP__) || defined(__DOS__)
-#    ifndef __DOS__
-#        define __DOS__
-#    endif
-    /* define it if it hadn't been done by configure yet */
-#    if !defined(wxSIZE_T_IS_UINT) && !defined(wxSIZE_T_IS_ULONG)
-#        ifdef __DJGPP__
-#            define wxSIZE_T_IS_ULONG
-#        endif
-#    endif
-
 /*
    OS: then test for generic Unix defines, then for particular flavours and
        finally for Unix-like systems
@@ -369,7 +354,6 @@
  */
 #if ( defined( __GNUWIN32__ ) || defined( __MINGW32__ ) || \
     ( defined( __CYGWIN__ ) && defined( __WINDOWS__ ) ) ) && \
-    !defined(__DOS__) && \
     !defined(__WXMOTIF__) && \
     !defined(__WXX11__)
 #    include "wx/msw/gccpriv.h"

include/wx/wxcrtbase.h

@@ -228,7 +228,7 @@ extern unsigned long android_wcstoul(const wchar_t *nptr, wchar_t **endptr, int
 
 /* define wxCRT_StricmpA/W and wxCRT_StrnicmpA/W for various compilers */
 
-#if defined(__BORLANDC__) || defined(__DJGPP__)
+#if defined(__BORLANDC__)
     #define wxCRT_StricmpA stricmp
     #define wxCRT_StrnicmpA strnicmp
 #elif defined(__VISUALC__)