Don't try to include modern C++ headers when building C++ Builder

C++ Builder6 doesn't have unordered_map, so only #include those std C++
headers if/where we actually need them.

src/sbbs3/sbbs.h

@@ -26,11 +26,6 @@
 /* Standard library headers */
 /****************************/
 
-#if defined(__cplusplus)
-	#include <string>
-	#include <unordered_map>
-#endif
-
 /***************/
 /* OS-specific */
 /***************/
@@ -382,6 +377,9 @@ typedef struct js_callback {
 /* Synchronet Node Instance class definition */
 #if defined(__cplusplus) && defined(JAVASCRIPT)
 
+#include <string>
+#include <unordered_map>
+
 struct mouse_hotspot {		// Mouse hot-spot
 	char	cmd[128];
 	int	y;