Improve support for NetBSD (#944)

- fix gcc version check for FL_DEPRECATED macro

- fix #include for select() on NetBSD < 3.0 (#944)

For more info please see GitHub Issue #944

FL/fl_attr.h

@@ -1,7 +1,7 @@
 /*
  * Function attribute declarations for the Fast Light Tool Kit (FLTK).
  *
- * Copyright 1998-2023 by Bill Spitzak and others.
+ * Copyright 1998-2024 by Bill Spitzak and others.
  *
  * This library is free software. Distribution and use rights are outlined in
  * the file "COPYING" which should have been included with this file.  If this
@@ -168,11 +168,11 @@
 #endif
 #endif /* gcc 4.5.0 */
 
-#if FL_GCC_VERSION > 30100 /* gcc 3.1.0 */
+#if FL_GCC_VERSION >= 30400 /* gcc 3.4.0 */
 #ifndef FL_DEPRECATED
 #define FL_DEPRECATED(msg, func) func __attribute__((deprecated))
 #endif
-#endif /* gcc 3.1.0 */
+#endif /* gcc 3.4.0 */
 
 #endif /* __GNUC__ */
 

src/drivers/Unix/Fl_Unix_Screen_Driver.H

@@ -31,6 +31,18 @@ static pollfd *pollfds = 0;
 #      include <sys/select.h>
 #    endif /* HAVE_SYS_SELECT_H */
 
+// NetBSD before version 3.0 declares select() in "unistd.h" (#944):
+// https://man.netbsd.org/NetBSD-2.1/select.2
+
+#    if defined(__NetBSD__)
+#      include <sys/param.h>  // For '__NetBSD_Version__' definition
+#      if defined(__NetBSD_Version__) && (__NetBSD_Version__ < 300000000)
+#        include <sys/types.h>
+#        include <sys/time.h>
+#        include <unistd.h>
+#      endif  // __NetBSD_Version__
+#    endif  // __NetBSD__
+
 #    define POLLIN 1
 #    define POLLOUT 4
 #    define POLLERR 8