docs: fix syntax highlighting of code blocks

And various other cleanups

Change-Id: I240badc5358c09f006c2a22d4706ce373f2dd188
diff --git a/docs/manpages/nfd-autoreg.rst b/docs/manpages/nfd-autoreg.rst
index 33e94bd..3ce898a 100644
--- a/docs/manpages/nfd-autoreg.rst
+++ b/docs/manpages/nfd-autoreg.rst
@@ -1,12 +1,10 @@
 nfd-autoreg
 ===========
 
-Usage
------
+Synopsis
+--------
 
-::
-
-    nfd-autoreg --prefix=</autoreg/prefix> [--prefix=</another/prefix>] ...
+**nfd-autoreg** --prefix=</autoreg/prefix> [--prefix=</another/prefix>]...
 
 Description
 -----------