legacy junk compatibility grab-bag

- add the rest of the junk traditionally in sys/param.h
- add prototypes for some nonstandard functions
- add _GNU_SOURCE to their source files so the compiler can check proto

include/termios.h

@@ -32,6 +32,11 @@ int tcflow (int, int);
 
 pid_t tcgetsid (int);
 
+#ifdef _GNUS_SOURCE
+void cfmakeraw(struct termios *);
+int cfsetspeed(struct termios *, speed_t);
+#endif
+
 #ifdef __cplusplus
 }
 #endif