preproc_cpp test for testing preprocessor and C++

Move C++ comment testing into here.
See 7a9bf3307f.

Examples/test-suite/preproc.i

@@ -373,6 +373,7 @@ int methodX(int x) { return x+100; }
 /*
    Comma in macro - https://github.com/swig/swig/issues/974 (for C comments)
    and https://github.com/swig/swig/pull/1166 (for //)
+   Also see preproc_cpp.i
 */
 %inline %{
 #define swig__attribute__(x)

Examples/test-suite/preproc_cpp.i

@@ -0,0 +1,36 @@
+%module preproc_cpp
+
+
+// Comma in macro - https://github.com/swig/swig/issues/974 (for /* */)
+// and https://github.com/swig/swig/pull/1166 (for //)
+// Also see preproc.i
+%inline %{
+#define swig__attribute__(x)
+#define TCX_PACKED(d) d swig__attribute__ ((__packed__))
+
+
+TCX_PACKED (typedef struct tcxMessageTestImpl
+{
+    int mHeader; /**< comment */
+}) tcxMessageTest;
+
+
+TCX_PACKED (typedef struct tcxMessageBugImpl
+{
+    int mBid; /**< Bid price and size, check PresentMap if available in message */
+}) tcxMessageBug;
+
+
+TCX_PACKED (typedef struct tcxMessageTestImpl2
+{
+    int mHeader; ///< comment
+}) tcxMessageTest2;
+
+
+TCX_PACKED (typedef struct tcxMessageBugImpl2
+{
+    int mBid; ///< Bid price and size, check PresentMap if available in message
+}) tcxMessageBug2;
+
+
+%}

Examples/test-suite/python/preproc_cpp_runme.py

@@ -0,0 +1,4 @@
+import preproc_cpp
+
+t1 = preproc_cpp.tcxMessageTest()
+t2 = preproc_cpp.tcxMessageBug()