Log Message:
tex-memoir{,-doc}: update to 3.7n

3.7l
Minute change to memoir in preparation for the October kernel update.

3.7m
In preparation for the LaTeX format/kernel update (2020/10/01) several
class hook features have been changed to use these new features, see
the manuals for lthooks, ltfilehook, ltshipout for details on these
new hooks.

3.7n
A bit of an emergency update:

-- The new implementations for the \AtEndPackage and friends only
   require single #s not # doubling as in the old implementation. That
   is not backwards compatible. # doubling now forced in the new
   implementation as well.