Peter M. Groen / libmodbus

Thank you @pboettch for initial proposal.

Useful functions when you are confronted with equipment which does
not respect the protocol, which behaves strangely or when you wish
to move away from the standard.

Thank you @mhei for the great initial version.

Thanks to @peternewman

Since SPDX release 3.0 LGPL-2.1+ became LGPL-2.1-or-later. Hence
replace the deprecated identifiers.

Thanks to @JCWren

Current code could dereference NULL pointer in case an inner
malloc fails. Check for this and exit gracefully.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

EMBBADCRC, not EMBADCRC

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

This replaces the lengthy license text headers with a short
and standardized license tag. See http://spdx.org for details.

This is useful e.g. for license compliance tools which scan
through files and generate a report of the licenses used
in a project.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

Thanks to Marjan Tomas

Thank you AlexMaz.

Thanks to Jan Kardell.

- change return argument from void to int
- update documentation