docs: kdoc_output: Change the logic to handle man highlight

docs: kdoc_output: Change the logic to handle man highlight

The code inside ManFormat code to output man pages is too simple:
it produces very bad results when the content has tables or code
blocks.

Change the way lines are parsed there to allow adding extra
logic to handle some special cases.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <6ae2301a40b3fcb4381dd9dda8c75d14f9616b46.1772810752.git.mchehab+huawei@kernel.org>