to recognize the long form of defstruct (defstruct (name (:constructor ....)))
export-accessors/slots available for defstruct
export-constructors available for defstruct
use alexandria:symbolicate rather than concatenate-symbols
added the documentation about structures.
Removed useless import rcurry and when-let from alexandria.
Replace hard tabs into normal spaces.
Fix up needless newlines.
Added `plan' to a test file.
Remove needless spaces.