termios: Consolidate local mode definitions

This patch consolidates the termios symbolic constants used for local
mode with c_lflag member on its own header.  The Linux generic implementation
values match the kernel UAPI and each architecture with deviate values
have their own implementation (in this case alpha, mips, and powerpc).

No semantic change is expected, checked on a build against x86_64-linux-gnu,
alpha-linux-gnu, mips64-linux-gnu, and sparc64-linux-gnu.

	* sysdeps/unix/sysv/linux/Makefile (sysdep_headers): Add
	termios-c_lflag.h.
	* sysdeps/unix/sysv/linux/bits/termios-c_lflag.h: New file.
	* sysdeps/unix/sysv/linux/alpha/bits/termios-c_lflag.h: Likewise.
	* sysdeps/unix/sysv/linux/mips/bits/termios-c_lflag.h: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/bits/termios-c_lflag.h: Likewise.
	* sysdeps/unix/sysv/linux/bits/termios.h (ISIG, ISCANON, ECHO, ECHOE,
	ECHOK, ECHONL, NOFLSH, TOSTOP, IEXTEN): Move to termios-c_lflag.h.
	[__USE_MISC || (__USE_XOPEN && !__USE_XOPEN2K)] (XCASE): Likewise.
	[__USE_MISC] (ECHOCTL, ECHOPRT, ECHOKE, FLUSHO, PENDIN, EXTPROC):
	Likewise.
	* sysdeps/unix/sysv/linux/alpha/bits/termios.h: Likewise.
	* sysdeps/unix/sysv/linux/mips/bits/termios.h: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/bits/termios.h: Likewise.
	* sysdeps/unix/sysv/linux/sparc/bits/termios.h: Likewise.