Fix static buffer overrrun (issue #443)

result[6] is a fixed array of size 6, but in the process
of copying data into it, we clobber the last allocated byte.

Simplify some of the code by not calling redundant functions.

src/language.c

@@ -601,7 +601,6 @@ tmbstr tidyNormalizedLocaleName( ctmbstr locale )
     uint i;
     uint len;
     static char result[6] = "xx_yy";
-    char character[1];
     tmbstr search = strdup(locale);
     search = TY_(tmbstrtolower)(search);
 
@@ -622,27 +621,28 @@ tmbstr tidyNormalizedLocaleName( ctmbstr locale )
      junk language that doesn't exist and won't be set. */
 
     len = strlen( search );
-    len = len <= 5 ? len : 5;
+    len = ( len <= 5 ? len : 5 );
 
-    for ( i = 0; i <= len; i++ )
+    for ( i = 0; i < len; i++ )
     {
         if ( i == 2 )
         {
             /* Either terminate the string or ensure there's an underscore */
-            if (strlen( search) >= 5)
-                character[0] = '_';
-            else
-                character[0] = '\0';
-            strncpy( result + i, character, 1 );
+            if (len == 5) {
+                result[i] = '_';
+            }
+            else {
+                result[i] = '\0';
+                break;      /* no need to copy after null */
+            }
         }
         else
         {
-            strncpy( result + i, search + i, 1);
-            result[i] = tolower( result[i] );
+            result[i] = tolower( search[i] );
         }
     }
 
-    if ( search ) free( search );
+    free( search );
     return result;
 }