Pull in more Linux definitions from original build files

xpdevplus.h.in

 #ifndef XPDEV_PLUS_H
 #define XPDEV_PLUS_H
 
+#ifdef __linux__
+#define POSIX_C_SOURCE 200809L
+#define _DEFAULT_SOURCE
+#define _BSD_SOURCE
+#define SPEED_MACROS_ONLY 
+#define _GNU_SOURCE 
+#define _FILE_OFFSET_BITS =64
+#endif
+
 #cmakedefine WITH_SDL
 #cmakedefine N_CURSES_LIB
 #cmakedefine HAS_INTTYPES_H