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.

configure

@@ -12961,7 +12961,7 @@ else
 fi
 
   fi
-  # LibreSSL does not have SSL_CTX_set_cert_cb().
+  # Function introduced in OpenSSL 1.0.2, not in LibreSSL.
   for ac_func in SSL_CTX_set_cert_cb
 do :
   ac_fn_c_check_func "$LINENO" "SSL_CTX_set_cert_cb" "ac_cv_func_SSL_CTX_set_cert_cb"

configure.ac

@@ -1377,8 +1377,7 @@ if test "$with_ssl" = openssl ; then
      AC_SEARCH_LIBS(CRYPTO_new_ex_data, [eay32 crypto], [], [AC_MSG_ERROR([library 'eay32' or 'crypto' is required for OpenSSL])])
      AC_SEARCH_LIBS(SSL_new, [ssleay32 ssl], [], [AC_MSG_ERROR([library 'ssleay32' or 'ssl' is required for OpenSSL])])
   fi
-  # Function introduced in OpenSSL 1.0.2. LibreSSL does not have
-  # SSL_CTX_set_cert_cb().
+  # Function introduced in OpenSSL 1.0.2, not in LibreSSL.
   AC_CHECK_FUNCS([SSL_CTX_set_cert_cb])
   # Functions introduced in OpenSSL 1.1.0. We used to check for
   # OPENSSL_VERSION_NUMBER, but that didn't work with 1.1.0, because LibreSSL

meson.build

@@ -1270,7 +1270,7 @@ if sslopt in ['auto', 'openssl']
       ['CRYPTO_new_ex_data', {'required': true}],
       ['SSL_new', {'required': true}],
 
-      # Functions introduced in OpenSSL 1.0.2, not in LibreSSL.
+      # Function introduced in OpenSSL 1.0.2, not in LibreSSL.
       ['SSL_CTX_set_cert_cb'],
 
       # Functions introduced in OpenSSL 1.1.0. We used to check for