symbol not coding-system-p
Versions: 21.1, 21.5
`coding-system-p' documentation says:
Coding systems are normally identified using a symbol, and the
symbol is accepted in place of the actual coding system object whenever
a coding system is called for.
Emacs does the same, and there is code depending on it. However,
(coding-system-p 'iso-8859-1) => nil