Displaying U+02BC in texinfo

[Paul Eggert]

While editing the GNU Emacs manual to contain the word “Baháʼí” (spelled with
U+02BC MODIFIER LETTER APOSTROPHE) I noticed that the texi2pdf output omitted
the character. Proposed patch attached (which also fixes a comment typo).

This isn't urgent, since we decided to go with “Bahá'í” instead, as this renders
the same as as “Bahá’í” (with U+2019 RIGHT SINGLE QUOTATION MARK) which is also
a common spelling and is good enough for Emacs. See:

https://debbugs.gnu.org/41100

texinfo-fix.txt
Description: Text document