id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	difficulty
1820	Clean up C preprocessor macros	felix winkelmann		"We can replace `C_externimport` and `C_externexport` with `C_extern`.
Also, `C_fcall` can be removed. Possibly also `C_regparm` and `C_ccall` as these refer to obsolete features.

`C_TLS` was never used and should go.

Note: `C_externimport` and `C_externexport` are produced bz the compiler, so need to be retained for at least one release."	task	new	minor	someday	core libraries	5.3.0				easy