This patch fixes the following compiler warning:
mmcli-output.c:783:19: error: implicitly declaring library function 'strlen' with type 'unsigned long (const char *)' [-Werror,-Wimplicit-function-declaration]
aux = strlen (section_infos[field_infos[item_l->field].section].name);
^
In addition to the standard human-friendly output, we now allow a
machine-friendly key-value pair output, much easier to parse and use
by programs that look at the mmcli output.
This new key-value pair output should be treated as API from now on, so
third-party programs can assume the output is compatible from one
release to another.
