tools: Add -x option to specify delimiter for machine readable output

tools: Add -x option to specify delimiter for machine readable output

To support this, update printm() to replace ':' in format string with
options.machineseparator, which is a string but must contain a single
character.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
(Imported from commit 3b90e45bae555cc4a47fe9958b86628d41084868)