CheckStructHasMember: Add support for C++

Previously if headers required to check if a struct has a member can be
compiled with C++ compiler only, the check would fail because the C
compiler fails.  As a consequence, the result variable would be set to
false, even if the struct has that particular member.

Teach CHECK_STRUCT_HAS_MEMBER to accept a new optional argument LANGUAGE
that allows one to explicitly set the compiler to use.  The new
signature is therefore:

  CHECK_STRUCT_HAS_MEMBER (<struct> <member> <header> <variable>
                           [LANGUAGE <language>])

1 files changed, 9 insertions, 0 deletions

diff --git a/Tests/CMakeOnly/CheckStructHasMember/cm_cshm.h b/Tests/CMakeOnly/CheckStructHasMember/cm_cshm.h
new file mode 100644
index 0000000..82bb049
--- /dev/null
+++ b/Tests/CMakeOnly/CheckStructHasMember/cm_cshm.h
@@ -0,0 +1,9 @@
+#ifndef _CSHM_DUMMY_H
+#define _CSHM_DUMMY_H
+
+struct non_existent_struct;
+struct struct_with_member{
+    int member;
+};
+
+#endif