cleanned test_capi example

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

test_capi/README.txt

@@ -0,0 +1,25 @@
+WARNING: this example still uses the old Z3 (version 3.x) C API. 
+The current version is backward compatible. 
+
+1) Using Visual Studio (with Z3 source code release)
+
+The test_capi application is automatically built when the z3-prover.sln is processed. The following command should be used to compile z3-prover.sln in the Z3 root directory
+
+        msbuild /p:configuration=external
+
+The maxsat executable is located at
+    
+        ..\external\test_capi
+
+2) Using gcc (on Linux or OSX)
+
+Use 'build.sh' to build the test application using gcc. 
+
+You must install Z3 before running this example.
+To install Z3, execute the following command in the Z3 root directory.
+
+  sudo make install
+
+Use 'build.sh' to build the test application using gcc. 
+It generates the executable 'test_capi'.
+