coccinelle patch suggestion

[Dan Nicolaescu]

Many lisp functions are declared in header files using the EXFUN macro,
like this:
EXFUN (Finteractive_form, 1);

this might have been good when wanting to support both pre-standard C
and standard  C, but we don't support the former anymore.

And EXFUN just adds an unneeded level of obfuscation that doesn't help
code readability.

It seems that with coccinelle it should be easy to create a patch that
replaces all EXFUN usages with the correct declaration, and then EXFUN
can be removed.