finshed a first round of test, starting examples

test/set/post_post-error.cpp

@@ -0,0 +1,18 @@
+
+// Test multiple post error (for free func, but same for all contracts).
+
+#include <boost/contract/free_function.hpp>
+#include <boost/contract/scoped.hpp>
+
+void f() {
+    boost::contract::scoped c = boost::contract::free_function()
+        .postcondition([] {})
+        .postcondition([] {}) // Error (multiple post).
+    ;
+}
+
+int main() {
+    f();
+    return 0;
+}
+