apps/testing/cxxtest: Add a README file.

testing/cxxtest/README.txt

@@ -0,0 +1,34 @@
+README
+======
+
+  This is a test of the C++ standard library.  At present a port of the uClibc++
+  C++ library is available.  Due to licensing issues, the uClibc++ C++ library
+  is not included in the NuttX source tree by default, but must be installed
+  (see the README.txt file in the uClibc++ download package for installation).
+
+  The uClibc++ test includes simple test of:
+
+    - iostreams,
+    - STL,
+    - RTTI, and
+    - Exceptions
+
+  Example Configuration Options
+  -----------------------------
+    CONFIG_TESTINGCXXTEST=y - Eanbles the example
+    CONFIG_TESTINGCXXTEST_CXXINITIALIZE=y - By default, if CONFIG_HAVE_CXX
+      and CONFIG_HAVE_CXXINITIALIZE are defined, then this example
+      will call the NuttX function to initialize static C++ constructors.
+      This option may be disabled, however, if that static initialization
+      was performed elsewhere.
+
+  Other Required Configuration Settings
+  -------------------------------------
+  Other NuttX setting that are required include:
+
+    CONFIG_HAVE_CXX=y
+    CONFIG_HAVE_CXXINITIALIZE=y
+    CONFIG_UCLIBCXX=y
+
+  Additional uClibc++ settings may be required in your build environment.
+