Revert "Issue3383: old-straight-flag + smaller Stem.thickness gives no output and huge over"

This reverts commit 04ce84386dc022316c347ee0c5049c852eea3421.

This is a temporary measure for dealing with issue 3432.
issue 3441: banjo example should use Staff + TabStaff
Revert "Make EventClass hierarchy a property of Global context"

This reverts commit ae2db5b21bf232f5145f3a3e091689c8fc7247e9.

Conflicts:
	lily/context-scheme.cc
	lily/global-context.cc
	lily/music.cc
	lily/part-combine-iterator.cc
	scm/define-event-classes.scm
	scm/document-music.scm

Independently introduced conflict:
	lily/footnote-engraver.cc

Also fix tabs reintroduced by revert
Reinitialize all-event-classes and all-grob-descriptions after session
Issue 3439: Create a two-argument form of define-event-class

This definition of define-event-class just specifies the event class
symbol itself as well as its immediate parent class.  Redefining
existing event classes is not (yet?) supported.
Issue 3440: Avoid infinite recursion in Emacs' LilyPond-mode for percent in filenames

When using a file name like "Mazurek D%85browskiego.ly", using C-c C-l
in LilyPond-mode resulted in

let: Variable binding depth exceeds max-specpdl-size

errors.  This fixes the problem by not doing further percent expansion
on the file name in `LilyPond-command-expand'.
Issue 3446: Use \translate-scaled in accordion-discant-symbols.ly

Otherwise prospective changes of font-size lead to ugly results.
Run scripts/auxiliar/makelsr.py
Issue 3451: anacrucis -> anacrusis.