MFC r367757, r367756, r367759, r367769:

Improve readability of the lists of options

• Sort options alphabetically
• Add missing arguments (e.g., "list" to -a)
• Adjust the width of Bl

Clean up the synopsis section & fix mandoc warnings

The synopsis section had two very similar entries. The flags documented by
the first one were a strict subset of the second one. Let's just keep only
the second entry for simplicity.

Add an example for the -s flag

Partially revert r367756 (chpass(1) synopsis changes)

Let's have two entries in the synopsis:

• chpass now lists options which can be used for non-NIS-specific functionalities.
• ypchpass additionally lists the NIS-specific flags.

Technically, it is an artificial distinction, as chpass and ypchpass behave
identically. Nevertheless, it might help navigating the synopsis section.

Reviewed by: imp