ada: Fix Ada.Text_IO.Delete with "encoding=8bits" form

Before this patch, on Windows, file with non-ASCII Latin1 names could be created
with Ada.Text_IO.Create by passing "encoding=8bits" through the Form
parameter and a Latin1-encoded string through the Name parameter,
but calling Ada.Text_IO.Delete on them raised an illegitimate exception.

This patch fixes this by making the wrappers of the unlink system function
aware of the encoding value passed through the Form parameter. It also
removes an unnecessary curly-brace block.

gcc/ada/

	* adaint.c (__gnat_unlink): Add new parameter and fix text
	conversion on Windows. Remove unnecessary curly braces.
	* adaint.h (__gnat_unlink): Add new parameter.
	* libgnat/i-cstrea.ads (unlink): Adapt to __gnat_unlink signature
	change.
	* libgnat/i-cstrea.adb (unlink): New Subprogram definition.
	* libgnat/s-crtl.ads (unlink): Adapt to __gnat_unlink signature
	change.
	* libgnat/s-fileio.adb (Delete): Pass encoding argument to unlink.

gcc/ada/adaint.c

@@ -747,15 +747,19 @@ __gnat_os_filename (char *filename ATTRIBUTE_UNUSED,
 /* Delete a file.  */
 
 int
-__gnat_unlink (char *path)
+__gnat_unlink (char *path, int encoding ATTRIBUTE_UNUSED)
 {
 #if defined (__MINGW32__) && ! defined (__vxworks) && ! defined (IS_CROSS)
-  {
-    TCHAR wpath[GNAT_MAX_PATH_LEN];
+  TCHAR wpath[GNAT_MAX_PATH_LEN];
 
+  if (encoding == Encoding_Unspecified)
     S2WSC (wpath, path, GNAT_MAX_PATH_LEN);
-    return _tunlink (wpath);
-  }
+  else if (encoding == Encoding_UTF8)
+    S2WSU (wpath, path, GNAT_MAX_PATH_LEN);
+  else
+    S2WS (wpath, path, GNAT_MAX_PATH_LEN);
+
+  return _tunlink (wpath);
 #else
   return unlink (path);
 #endif

gcc/ada/adaint.h

@@ -172,7 +172,7 @@ extern int    __gnat_open_new_temp		   (char *, int);
 extern int    __gnat_mkdir			   (char *, int);
 extern int    __gnat_stat			   (char *,
 						    GNAT_STRUCT_STAT *);
-extern int    __gnat_unlink                        (char *);
+extern int    __gnat_unlink                        (char *, int encoding);
 extern int    __gnat_rename                        (char *, char *);
 extern int    __gnat_chdir                         (char *);
 extern int    __gnat_rmdir                         (char *);

gcc/ada/libgnat/i-cstrea.adb

@@ -130,4 +130,13 @@ package body Interfaces.C_Streams is
       return C_setvbuf (stream, buffer, mode, size);
    end setvbuf;
 
+   ------------
+   -- unlink --
+   ------------
+
+   function unlink (filename : chars) return int is
+   begin
+      return System.CRTL.unlink (filename);
+   end unlink;
+
 end Interfaces.C_Streams;

gcc/ada/libgnat/i-cstrea.ads

@@ -197,8 +197,7 @@ package Interfaces.C_Streams is
    function ungetc (c : int; stream : FILEs) return int
      renames System.CRTL.ungetc;
 
-   function unlink (filename : chars) return int
-     renames System.CRTL.unlink;
+   function unlink (filename : chars) return int;
 
    ---------------------
    -- Extra functions --

gcc/ada/libgnat/s-crtl.ads

@@ -220,7 +220,8 @@ package System.CRTL is
    function ungetc (c : int; stream : FILEs) return int;
    pragma Import (C, ungetc, "ungetc");
 
-   function unlink (filename : chars) return int;
+   function unlink (filename : chars;
+     encoding : Filename_Encoding := Unspecified) return int;
    pragma Import (C, unlink, "__gnat_unlink");
 
    function open (filename : chars; oflag : int) return int;

gcc/ada/libgnat/s-fileio.adb

@@ -350,6 +350,7 @@ package body System.File_IO is
       declare
          Filename : aliased constant String := File.Name.all;
          Is_Temporary_File : constant Boolean := File.Is_Temporary_File;
+         Encoding : constant CRTL.Filename_Encoding := File.Encoding;
 
       begin
          Close (File_Ptr);
@@ -360,7 +361,7 @@ package body System.File_IO is
          --  it's a temporary file, then closing it already unlinked it.
 
          if not Is_Temporary_File then
-            if unlink (Filename'Address) = -1 then
+            if System.CRTL.unlink (Filename'Address, Encoding) = -1 then
                raise Use_Error with OS_Lib.Errno_Message;
             end if;
          end if;