#11454: Reduce email module load time, improve surrogate check efficiency.

The new _has_surrogates code was suggested by Serhiy Storchaka.  See
the issue for timings, but it is far faster than any other alternative,
and also removes the load time that we previously incurred from compiling
the complex regex this replaces.
#18311: fix typo.
Merge #18311: fix typo.