w32: Always use Unicode for console input and output.

* common/init.c (_init_common_subsystems) [W32]: Set the codepage to
UTF-8 for input and putput.  Switch gettext to UTF-8.
* g10/gpg.c (utf8_strings) [W32]: Make sure this is always set.
--

With this patch the former patch to use ReadConsoleW and WriteConsoleW
in ttyio.c are kind of superfluous because the ANSI version of these
functions are also able to read/write UTF-8 directly given the console
code page has been set correctly.  However, this seems to work only
with recent versions of Windows-10.

GnuPG-bug-id: 4365
(cherry picked from commit 8c41b8aac3)
Removed changes for "gpgconf --show-codepages" of the original patch.

g10/gpg.c

@@ -970,7 +970,13 @@ static struct debug_flags_s debug_flags [] =
 
 int g10_errors_seen = 0;
 
-static int utf8_strings = 0;
+static int utf8_strings =
+#ifdef HAVE_W32_SYSTEM
+  1
+#else
+  0
+#endif
+  ;
 static int maybe_setuid = 1;
 
 static char *build_list( const char *text, char letter,
@@ -3308,7 +3314,11 @@ main (int argc, char **argv)
 	    opt.verify_options&=~VERIFY_SHOW_NOTATIONS;
 	    break;
 	  case oUtf8Strings: utf8_strings = 1; break;
-	  case oNoUtf8Strings: utf8_strings = 0; break;
+	  case oNoUtf8Strings:
+#ifdef HAVE_W32_SYSTEM
+            utf8_strings = 0;
+#endif
+            break;
 	  case oDisableCipherAlgo:
             {
               int algo = string_to_cipher_algo (pargs.r.ret_str);