Do not use stdbool.h.
Add some comments for linked list functions.

And thus be able to fix stupid mistakes.  Could we use past tense in the
commit message body? I don't know/care.
Probably got Makefile right this time.

C builds are cumbersome.
Add syntax.h.

Contains definitions of various syntactic elements.
Fixes to linked list.

I've written it as if list->car was a heap-allocated field of nodes,
where, in fact they are just static structs.