Updates needed for build pages

[miken32]

Recent changes in #203 were very helpful, thanks! We are starting a plan to update from 18 to 22 so the timing was good for us. A couple of things I noticed while re-reading these pages for the first time in years:

• documentation for menuselect still mentions voicemail options as a category
• list of make targets is incomplete (e.g. missing install-headers)
• no mention of the bundled version of libjwt or jansson (esp. when one should bundle vs use system versions)

[gtjoseph]

Thanks for the report. We'll get it updated shortly.