Fix -e et al when redirecting to NUL

Redirecting ansicon to NUL would still write to the console, as NUL is
regarded as a character device.  Export IsConsoleHandle and use that
instead of _isatty.

acrt.def

@@ -1,6 +1,7 @@
 EXPORTS
 __iob_func
 _fileno
+_get_osfhandle
 _iob
 _isatty
 _setmode

ansicon.c

@@ -92,6 +92,9 @@
 
   v1.84, 7 May, 2018:
     import the DLL.
+
+  v1.85, 22 August, 2018:
+    use IsConsoleHandle for my_fputws, to distinguish NUL.
 */
 
 #define PDATE L"22 August, 2018"
@@ -140,7 +143,7 @@ static HANDLE hConOut;
 // heck, DIY.
 int my_fputws( const wchar_t* s, FILE* f )
 {
-  if (_isatty( _fileno( f ) ))
+  if (IsConsoleHandle( (HANDLE)_get_osfhandle( _fileno( f ) ) ))
   {
     DWORD written;
     WriteConsole( hConOut, s, (DWORD)wcslen( s ), &written, NULL );

ansicon.h

@@ -89,6 +89,7 @@ typedef struct IMAGE_COR20_HEADER
 #define EXTERN __declspec(dllexport) extern
 #endif
 
+EXTERN BOOL IsConsoleHandle( HANDLE );
 EXTERN int ProcessType( LPPROCESS_INFORMATION, PBYTE*, BOOL* );
 BOOL   Wow64Process( HANDLE );
 

readme.txt

@@ -340,7 +340,8 @@ Version History
     Legend: + added, - bug-fixed, * changed.
 
     1.85 - 22 August, 2018:
-    - fix wrap issues with a buffer bigger than the window.
+    - fix wrap issues with a buffer bigger than the window;
+    - fix -e et al when redirecting to NUL.
 
     1.84 - 11 May, 2018:
     - close the flush handles on detach;
@@ -605,6 +606,7 @@ Acknowledgments
     Vincent Fatica for pointing out \e[K was not right.
     Nat Kuhn for pointing out the problem with report cursor position.
     Michel Kempeneers for discovering the buffer wrap issue.
+    Jean-Luc Gautier for pointing out the problem with redirecting -e to NUL.
 
     Thiadmer Riemersma for the nearest color algorithm.