Backport the inlines for cfsetspeed and tcdrain.

This fixes some issues with using boost's asio (which wrongly assumes
_BSD_SOURCE implies that these things are available) following our
change from -isystem to --sysroot.

Test: Manual, check that we can build when using cfsetspeed on ICS.
Bug: android/ndk#302
Change-Id: Iab50221e4864f9a09a8fb00691252170eb6e8d09
(cherry picked from commit 3b59037)

ndk/platforms/android-9/include/sys/cdefs.h

@@ -86,6 +86,12 @@
 #define	__static_cast(x,y)	(x)y
 #endif
 
+#if defined(__cplusplus)
+#define __BIONIC_CAST(_k,_t,_v) (_k<_t>(_v))
+#else
+#define __BIONIC_CAST(_k,_t,_v) ((_t) (_v))
+#endif
+
 /*
  * The __CONCAT macro is used to concatenate parts of symbol names, e.g.
  * with "#define OLD(foo) __CONCAT(old,foo)", OLD(foo) produces oldfoo.

ndk/platforms/android-9/include/termios.h

@@ -108,6 +108,18 @@ static __inline__ void cfmakeraw(struct termios *s)
     s->c_cflag |= CS8;
 }
 
+static __inline int cfsetspeed(struct termios* s, speed_t speed) {
+  // TODO: check 'speed' is valid.
+  s->c_cflag = (s->c_cflag & ~CBAUD) | (speed & CBAUD);
+  return 0;
+}
+
+static __inline int tcdrain(int fd) {
+  // A non-zero argument to TCSBRK means "don't send a break".
+  // The drain is a side-effect of the ioctl!
+  return ioctl(fd, TCSBRK, __BIONIC_CAST(static_cast, unsigned long, 1));
+}
+
 __END_DECLS
 
 #endif /* _TERMIOS_H_ */