Changing the behavior of the <error> function.
The funciton now requires a bunch of arguments, and interacts with the C-error continuation.
The change is not backward compatible, since it is no longer sufficient to pass just a string to <error>. The simplest way to update source files is to change
[error <some-str>]
to
[error 'misc VARNAME <some-str>]
if the expression appears inside the definition of a function being bound to a variable. In other places, just use
[error 'misc ("(don't know/don't care)") <some-str>]
or something similar.