Rework the text to numeric conversion routines so that they work with either

UTF8 or UTF16 and do not require a NULL terminator.  This allowed text to
numeric conversion without reallocating the string.

FossilOrigin-Name: 14eed3a0e0a45c6f2904a3a134aa27c159916f7b

src/test1.c

@@ -1235,7 +1235,7 @@ static int sqlite3_mprintf_int64(
     return TCL_ERROR;
   }
   for(i=2; i<5; i++){
-    if( !sqlite3Atoi64(argv[i], &a[i-2]) ){
+    if( !sqlite3Atoi64(argv[i], &a[i-2], 1000000, SQLITE_UTF8) ){
       Tcl_AppendResult(interp, "argument is not a valid 64-bit integer", 0);
       return TCL_ERROR;
     }