Fix bugs in termios library and cleanup code

This change fixes an issue with the tcflow() magic numbers that was
causing bash to freeze up on Linux. While auditing termios polyfills,
several other issues were identified with XNU/BSD compatibility.

Out of an abundance of caution this change undefines as much surface
area from libc/calls/struct/termios.h as possible, so that autoconf
scripts are less likely to detect non-POSIX teletypewriter APIs that
haven't been polyfilled by Cosmopolitan.

This is a *breaking change* for your static archives in /opt/cosmos if
you use the cosmocc toolchain. That's because this change disables the
ioctl() undiamonding trick for code outside the monorepo, specifically
because it'll lead to brittle ABI breakages like this. If you're using
the cosmocc toolchain, you'll need to rebuild libraries like ncurses,
readline, etc. Yes diamonds cause bloat. To work around that, consider
using tcgetwinsize() instead of ioctl(TIOCGWINSZ) since it'll help you
avoid pulling every single ioctl-related polyfill into the linkage.

The cosmocc script was specifying -DNDEBUG for some reason. It's fixed.

libc/calls/ttyname_r.c

@@ -32,6 +32,8 @@
 #include "libc/str/str.h"
 #include "libc/sysv/errfuns.h"
 
+#define FIODGNAME 0x80106678  // freebsd
+
 static textwindows dontinline int sys_ttyname_nt(int fd, char *buf,
                                                  size_t size) {
   uint32_t mode;
@@ -49,7 +51,6 @@ static textwindows dontinline int sys_ttyname_nt(int fd, char *buf,
 }
 
 static int ttyname_freebsd(int fd, char *buf, size_t size) {
-  const unsigned FIODGNAME = 2148558456;
   struct fiodgname_arg {
     int len;
     void *buf;