[metapost] Fix formatting glitches.

[Andreas Scherer]

Am 18.05.24 um 17:35 schrieb luigi scarso:
>   Committed revision 71291

Thanks! I have updated https://github.com/ascherer/mplibdir accordingly. 
It now has only about 20 commits that apply modifications from a second 
level of inspection (typos and CWEB-related code changes). Feel free to 
apply these in future revisions.

Cheers,
Andreas