#5187 Enhancement: Add command for 'Thin' Aikenheads

Back in June, I was typing up some Aiken-heads music for a client. We
ran into a problem shown in the attached PNG and LY files, where
white-head notes end up too dark at lower staff sizes. The problem was
resolved by using thin-variant Aiken heads. However, arriving at that
solution was a little challenging. With web searches, I was able to find
that the thin-variant note heads existed, but not how to access them. A
post to lilypond-user got good help from Abraham Lee.

https://lists.gnu.org/archive/html/lilypond-user/2017-06/msg00137.html

The solution was:

aikenHeadsThin = \set shapeNoteStyles = ##(doThin reThin miThin faThin
sol laThin tiThin)

[Anonymous]

From: Carl Sorensen

As much as I hate to have commands expand, I think given all of the other
shape note commands, we should probably go ahead and add a command
\aikenThinHeads (rather than \aikenHeadsThin -- all of the others end
with Heads) and \aikenThinHeadsMinor.

Thanks,

Carl

[Simon Albrecht]

I second that.

[Karlin High]

Issue 5198 added the \aikenThinHeads commands. That one has been fixed and closed; doing the same here.