There's only two places where we're using the C99 feature of array
designated initalizers. This feature seemingly wasn't included with
C++20 designated initalizers for classes and structs. The only two
places we were using this feature are suitably old and isolated that
it makes sense to just suppress the warning at the usage sites while
discouraging future array designated intializers in new code.
Some ports (like `bc` with history enabled) sensibly set the termios
character size to 8 bits.
Previously, we left the character size value (given by the bitmask
CSIZE) as zero by default (meaning 5 bits per character), and returned
ENOTIMPL whenever someone modified it. This was dumb.
This commit adds support for the various ECHO* lflags and fixes some
POSIX conformance issues around newline handling. Also included are
error messages when setting not implemented settings.
This non-POSIX header is used in Linux/BSD systems for storing the
default termios settings. This lets us setup new TTYs' `m_termios.c_cc`
in a nicer way than using a magic string.
