fix generic termios.h macro exposure/namespace issues

add EXTA, EXTB, CIBAUD, CMSPAR, XCASE macros and hide them as well as
CBAUD, ECHOCTL, ECHOPRT, ECHOKE, FLUSHO, PENDIN in standard mode.

the new macros are both in glibc termios.h and in linux asm/termbits.h,
the later also contains IBSHIFT and BOTHER, those were not added.

these are not standard macros, but some of them are in the reserved
namespace so could be exposed, the ones which are not reserved are
CIBAUD, CMSPAR and XCASE (which was removed in issue 6), the rest
got hidden to be consistent with glibc.

arch/generic/bits/termios.h

@@ -109,8 +109,6 @@ struct termios
 #define B3500000 0010016
 #define B4000000 0010017
 
-#define CBAUD    0010017
-
 #define CSIZE  0000060
 #define CS5    0000000
 #define CS6    0000020
@@ -133,12 +131,6 @@ struct termios
 #define TOSTOP 0000400
 #define IEXTEN 0100000
 
-#define ECHOCTL 0001000
-#define ECHOPRT 0002000
-#define ECHOKE 0004000
-#define FLUSHO 0010000
-#define PENDIN 0040000
-
 #define TCOOFF 0
 #define TCOON  1
 #define TCIOFF 2
@@ -153,8 +145,21 @@ struct termios
 #define TCSAFLUSH 2
 
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
+#define EXTA    0000016
+#define EXTB    0000017
+#define CBAUD   0010017
 #define CBAUDEX 0010000
+#define CIBAUD  002003600000
+#define CMSPAR  010000000000
 #define CRTSCTS 020000000000
+
+#define XCASE   0000004
+#define ECHOCTL 0001000
+#define ECHOPRT 0002000
+#define ECHOKE  0004000
+#define FLUSHO  0010000
+#define PENDIN  0040000
 #define EXTPROC 0200000
+
 #define XTABS  0014000
 #endif