fix minor namespace issues in termios.h

the output delay features (NL*, CR*, TAB*, BS*, and VT*) are
XSI-shaded. VT* is in the V* namespace reservation but the rest need
to be suppressed in base POSIX namespace.

unfortunately this change introduces feature test macro checks into
another bits header. at some point these checks should be simplified
by having features.h handle the "FTM X implies Y" relationships.

arch/powerpc64/bits/termios.h

@@ -53,6 +53,7 @@ struct termios {
 #define ONLRET 0000040
 #define OFILL  0000100
 #define OFDEL  0000200
+#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE) || defined(_XOPEN_SOURCE)
 #define NLDLY  0001400
 #define NL0    0000000
 #define NL1    0000400
@@ -74,6 +75,7 @@ struct termios {
 #define BSDLY  0100000
 #define BS0    0000000
 #define BS1    0100000
+#endif
 
 #define VTDLY  0200000
 #define VT0    0000000