hw/xwin: Use X_ATTRIBUTE_PRINTF where suggested for winerror.c

Also, fix the typoed name OsVenderVErrorF (sic), so it actually gets prototyped
and remove redundant declarations of it's prototype.

winerror.c: In function ‘OsVendorVErrorF’:
winerror.c:56:5: warning: function might be possible candidate for ‘gnu_printf’ format attribute [-Wmissing-format-attribute]
winerror.c: In function ‘winMessageBoxF’:
winerror.c:104:5: warning: function might be possible candidate for ‘gnu_printf’ format attribute [-Wmissing-format-attribute]

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Colin Harrison <colin.harrison@virgin.net>

hw/xwin/InitOutput.c

@@ -77,11 +77,6 @@ static void
  winClipboardShutdown(void);
 #endif
 
-#if defined(DDXOSVERRORF)
-void
- OsVendorVErrorF(const char *pszFormat, va_list va_args);
-#endif
-
 static Bool
  winCheckDisplayNumber(void);
 

hw/xwin/win.h

@@ -857,11 +857,13 @@ void
 
 #ifdef DDXOSVERRORF
 void
- OSVenderVErrorF(const char *pszFormat, va_list va_args);
+OsVendorVErrorF(const char *pszFormat, va_list va_args)
+_X_ATTRIBUTE_PRINTF(1, 0);
 #endif
 
 void
- winMessageBoxF(const char *pszError, UINT uType, ...);
+winMessageBoxF(const char *pszError, UINT uType, ...)
+_X_ATTRIBUTE_PRINTF(1, 3);
 
 #ifdef XWIN_NATIVEGDI
 /*

hw/xwin/winerror.c

@@ -36,10 +36,6 @@
 #include "win.h"
 
 #ifdef DDXOSVERRORF
-/* Prototype */
-void
- OsVendorVErrorF(const char *pszFormat, va_list va_args);
-
 void
 OsVendorVErrorF(const char *pszFormat, va_list va_args)
 {

hw/xwin/winprocarg.c

@@ -56,10 +56,6 @@ void
 void
  winLogVersionInfo(void);
 
-#ifdef DDXOSVERRORF
-void OsVendorVErrorF(const char *pszFormat, va_list va_args);
-#endif
-
 /*
  * Process arguments on the command line
  */