Fix some comments in ./configure and meson setup files

Fix some comments in ./configure and meson setup files

The comments referring to SSL_CTX_set_cert_cb() in ./configure and
./configure.ac were inconsistent, as `autoreconf -i` would show.  While
on it, fix a typo on a comment related to the same check in
meson.build.

Issue introduced in 8e278b6, that removed support for OpenSSL 1.0.1.
Per offlist report from Thomas Munro.