add platform check for std::is_trivially_copyable

 Yes, the template instantiation appears necessary for cmake to
 detect the type. If there's a better type for it than int, I'm
 open to suggestions.

cmake/platformChecks.cmake

@@ -7,6 +7,7 @@ include(CheckLibraryExists)
 include(CheckPrototypeDefinition)
 include(CheckStructHasMember)
 include(CheckSymbolExists)
+include(CheckCXXSymbolExists)
 include(CheckTypeSize)
 
 CHECK_INCLUDE_FILE("execinfo.h" HAVE_EXECINFO_H)
@@ -16,6 +17,10 @@ CHECK_TYPE_SIZE("max_align_t" MAX_ALIGN_T)
 
 set(CMAKE_EXTRA_INCLUDE_FILES "cstddef")
 CHECK_TYPE_SIZE("std::max_align_t" STD_MAX_ALIGN_T LANGUAGE CXX)
+set(CMAKE_EXTRA_INCLUDE_FILES "type_traits")
+set(CMAKE_REQUIRED_FLAGS "-std=c++11") # required for g++ <= 5
+CHECK_TYPE_SIZE("std::is_trivially_copyable<int>" STD_IS_TRIVIALLY_COPYABLE LANGUAGE CXX)
+set(CMAKE_REQUIRED_FLAGS)
 set(CMAKE_EXTRA_INCLUDE_FILES)
 
 CHECK_FUNCTION_EXISTS(strcasecmp HAVE_STRCASECMP)

cmake/platformChecks.h.in

@@ -8,6 +8,8 @@
 #cmakedefine HAVE_MAX_ALIGN_T
 #cmakedefine HAVE_STD_MAX_ALIGN_T
 
+#cmakedefine HAVE_STD_IS_TRIVIALLY_COPYABLE
+
 #cmakedefine01 IS_64BIT
 
 #cmakedefine01 HAVE_STRCASECMP

code/scripting/ade.h

@@ -5,6 +5,7 @@
 #define FS2_OPEN_ADE_H
 
 #include "globalincs/pstypes.h"
+#include "platformChecks.h"
 
 extern "C" {
 #include <lauxlib.h>
@@ -226,8 +227,9 @@ template<class StoreType>
 class ade_obj: public ade_lib_handle {
  public:
 	// Make sure that the stored type is compatible with our requirements
+#ifdef HAVE_STD_IS_TRIVIALLY_COPYABLE
 	static_assert(std::is_trivially_copyable<StoreType>::value, "ADE object types must be trivially copyable!");
-
+#endif
 	ade_obj(const char* in_name, const char* in_desc, const ade_lib_handle* in_deriv = NULL) {
 		ade_table_entry ate;