Fix [63325009a8]: \u0400 conversion to and from cesu-8 fails.

Author: jan.nijtmans

generic/tclEncoding.c

@@ -2595,7 +2595,7 @@ UtfToUtfProc(
 
 	    const char *saveSrc = src;
 	    src += len;
-	    if (!(flags & ENCODING_UTF) && !(flags & ENCODING_INPUT) && (ch > 0x3FF)) {
+	    if (!(flags & ENCODING_UTF) && !(flags & ENCODING_INPUT) && (ch > 0x7FF)) {
 		if (ch > 0xFFFF) {
 		    /* CESU-8 6-byte sequence for chars > U+FFFF */
 		    ch -= 0x10000;

tests/encoding.test

@@ -471,6 +471,9 @@ test encoding-15.31 {UtfToUtfProc -profile strict CESU-8 (bytes F0-F4 are invali
 test encoding-15.32 {UtfToUtfProc CESU-8 [2f22a7364d]} -body {
     encoding convertto cesu-8 \U1f600
 } -result \xED\xA0\xBD\xED\xB8\x80
+test encoding-15.33 {UtfToUtfProc CESU-8 [63325009a8]} -body {
+    encoding convertto utf-8 \u0400
+} -result \xD0\x80
 
 test encoding-16.1 {Utf16ToUtfProc} -body {
     set val [encoding convertfrom utf-16 NN]