Fix method accessors for inherits and abstracts

Closes PR 13798
Restore commented `for` loop

The bug this was blocked on seems to be fixed since the
tests now all pass.
added command-line demo
New Racket version 5.3.4.11.
Synch German string constants with latest.
Typo fix: "Encapsulted" -> "Encapsulated".
scribble docs typo
macro docs extraneous char
Fix error source location access for struct refactor.
Fix contracted TR build.
Fix type in error case
Fix TR contracts.
Turn off TR contracts.
fix a bug in is-a?

This bug has been in is-a? since at least 5.2; it turns some errors
into #f. Hopefully no code is actually relying on this bad behavior...
missed another spot for the vector => exn-info change

this fixes another bug in commit 3474d091
Fix Reference typos
move boolean to the last production to avoid breaking
the random generation tests
adjust syncheck tests to cope with test inputs
whose size is not known until the test suite runs
find the ryr-test failure and make a small example; also
make the ryr test print the entire url when it runs
missed a spot in 33b65f5ec