Add test showing c linkage working fine [#16]

unittests/c_linkage_test.cpp

@@ -0,0 +1,20 @@
+#include <chaiscript/chaiscript.hpp>
+
+
+extern "C"
+{
+  int dosomething(int i)
+  {
+    return i % 2;
+  }
+}
+
+int main()
+{
+
+  chaiscript::ChaiScript chai;
+  chai.add(chaiscript::fun(&dosomething), "dosomething");
+
+  return chai.eval<int>("dosomething(101)") == 101 % 2?EXIT_SUCCESS:EXIT_FAILURE;
+
+}