For a compatibility reasons (with other doc files and with RTD)
the `rtpengine.pod` and `rtpengine-recording.pod` file get
converted to the Markdown syntax.
The compilation of MD syntax synopsis files will work
using `ronn` application, which converts them to man pages.
Change-Id: I75b54a712786a0a237c51c702ed1a2cc09e3a033