Update 116_legacy_interface_definition.md (#308)
Update 116_legacy_interface_definition.md (#308)

* Update 116_legacy_interface_definition.md

Support constants defined in binary, octal, decimal, & hex.

Co-authored-by: Chris Lalancette <281cd07d7578d97c83271fbbf2faddb83ab3791c@openrobotics.org>
ros2/design,ros2/design,ros2/design,ros2/design,ros2/design