Make <sys/ttydefaults.h> more usable.

* TTYDEF_OFLAG referred to the BSD OXTABS constant instead of the Linux XTABS,
  so references to it wouldn't compile.

* CEOL was incorrect (compared to `stty -a`).

* ttydefchars wouldn't compile (removed rather than attempt to fix something
  of unclear utility).

Bug: http://b/63145226
Test: new test
Change-Id: I823e5eaab789cafd2eeea03f77ea553346822f74
diff --git a/tests/sys_ttydefaults_test.cpp b/tests/sys_ttydefaults_test.cpp
new file mode 100644
index 0000000..fa4f7c7
--- /dev/null
+++ b/tests/sys_ttydefaults_test.cpp
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+
+#include <sys/ttydefaults.h>
+#include <termios.h>
+
+TEST(sys_ttydefaults, flags) {
+  int i;
+  i = TTYDEF_IFLAG;
+  i = TTYDEF_OFLAG;
+  i = TTYDEF_LFLAG;
+  i = TTYDEF_CFLAG;
+  i = TTYDEF_SPEED;
+}
+
+TEST(sys_ttydefaults, correct_CEOL) {
+  ASSERT_EQ(_POSIX_VDISABLE, CEOL);
+}