Log message:
tex-latex-base-dev{,-doc}: update to 20210501pre1

In addition to LaTeX2e 2020-10-01 patch level 4, this pre-release
features the following changes:

2020-12-22  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * ltfssaxes.dtx (subsection{Changing to a new series}):
        Distangle series and shape update by delaying the font series
        and font shape merging

        Move the rollback info for \normalshape after its main definition
        otherwise it will not be undone

2020-12-22  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * ltfsstrc.dtx (subsection{General font loading}):
        Alter \selectfont to do the delayed merging of  font series
        and font shape

2020-12-27  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * letter.dtx (subsubsection{Page breaking control}):
        The \opening argument was splitting name and address using \\
        but did not allow to use \\[...] for this

2020-12-10  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * ltbibl.dtx (section{Bibliography Generation}):
        Delay any \cs{nocite} in the preamble instead of raising
        an error

2020-12-06  Johannes Braams  <Johannes.Braams at latex-project.org>

        * miscelaneous files: gh/428, gh/429 and gh/430 list a number of
        typing mistakes and missing documentation that have crept in over
        the years. The following files were affected and have been
        corrected:
        alltt.dtx, classes.dtx, doc.dtx, docstrip.dtx, fix-cm.dtx,
        fontdef.dtx, ifthen.dtx, inputenc.dtx, latex209.dtx,
        latexrelease.dtx, ltbibl.dtx, ltboxes.dtx, ltclass.dtx,
        ltcntrl.dtx, ltcounts.dtx, ltdefns.dtx, ltdirchk.dtx, ltexpl.dtx,
        ltfilehook.dtx, ltfiles.dtx, ltfinal.dtx, ltfloat.dtx,
        ltfntcmd.dtx, ltfssaxes.dtx, ltfssbas.dtx, ltfsscmp.dtx,
        ltfssdcl.dtx, ltfssini.dtx, ltfsstrc.dtx, lthooks.dtx,
        ltlength.dtx, ltlists.dtx, ltluatex.dtx, ltmath.dtx, ltmiscen.dtx,
        ltoutenc.dtx, ltoutput.dtx, ltpage.dtx, ltpageno.dtx,
        ltpictur.dtx, ltplain.dtx, ltsect.dtx, ltshipout.dtx,
        lttextcomp.dtx, ltvers.dtx, ltxdoc.dtx, ltxref.dtx, nfssfont.dtx,
        proc.dtx, slides.dtx, utf8ienc.dtx.

2020-12-04  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * ltfilehook.dtx (subsection{Declaring a file substitution}):
        Don't drop file substitution declarations when rolling back
        just render them no-ops

2020-12-04  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>
        Add a hook to \selectfont to be executed after the switch to the
        new font. This implements the functionality formerly in the everysel
        package.

2020-12-04  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * ltfinal.dtx (subsection{File substitutions}):
        Emulate everysel package

2020-12-04  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * ltfssini.dtx (subsection{Miscellaneous}):
        Setting up \f at series and \f at shape default values directly

2020-11-23  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * ltshipout.dtx:
        Check for both kernel and user hooks and execute if either is non-empty

2020-10-26  Frank Mittelbach  <Frank.Mittelbach at latex-project.org>

        * ltmiscen.dtx (subsection{Environments}):
        \enddocument should always start out in vmode