lttng-ust: add development manpages.
lttng-ust: add development manpages.

Closes: #12771 [via git-merge-pr]

coredumb/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,coredumb/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,coredumb/void-packages,NeoChontrix/void-packages,coredumb/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,coredumb/void-packages,NeoChontrix/void-packages,coredumb/void-packages