Add .gitignore file

termcodes: make VEOL2, VWERASE, VLNEXT, ECHOCTL, and ECHOKE optional

Change label name _ERR to LBL_ERR

Use DROPBEAR_PATH_DEVNULL instead of undefined _PATH_DEVNULL

more linting

remove K&R old style code

in order to remove K&R code in atomicio.c

now, vwrite comes from atomicio.h

in order to remove K&R code

Ignored are all files created when building from a git checkout as well as
anything deleted by 'make clean'.

Signed-off-by: Ben Gardner <gardner.ben@gmail.com>

My POSIX-like platform is missing some basic termcodes.
Make them optional.

Signed-off-by: Ben Gardner <gardner.ben@gmail.com>

_ERR is defined in stdio.h on my platform.

Signed-off-by: Ben Gardner <gardner.ben@gmail.com>

Support out-of-tree builds usign bundled libtom

When building out-of-tree we need both source and generated
folders in include paths to find both distributed and generated
headers.