move Sex to better types

Types, fns and vars are now written in another, better, more intuitive
and readable way.

Types:
"pointer to const char" is "* const char"
"array of pointers to volatile int" is "[* volatile int]"
Read left to right

Vars (as well as fn args, struct fields):
(var name type)
(struct vec3 ((x float) (y float) (z float))
(fn vec3-add ((v1 vec3) (v2 vec3)) vec3 ...)

Also fns are now have return types after arg list.

* is now must not be attached to any type name (or variable for that
matter)

tests/fmt-c-writer.scm

@@ -0,0 +1,114 @@
+;;; Types
+(test-group "fmt-writer"
+
+  (test
+   '(const int)
+   (walk-type '(const int)))
+
+  (test
+   '(%array (const char) 512)
+   (walk-type '(¤ const char 512)))
+
+  (test
+   '(%array (float 512))
+   (walk-type '(¤ (float 512))))
+
+  (test
+   '(%array (const char) 512)
+   (walk-type '(¤ (const char) 512)))
+
+  (test
+   '(%array (const char))
+   (walk-type '(¤ const char)))
+
+  (test
+   '(%array (const char))
+   (walk-type '(¤ (const char))))
+
+  (test
+   '(%array (float) 8)
+   (walk-type '(¤ float 8)))
+
+  (test
+   "Pointer to const char"
+   '(const char *)
+   (walk-type '(* const char)))
+
+  (test
+   "Const pointer to const char"
+   '(const char * const)
+   (walk-type '(const * const char)))
+
+  (test
+   '(%fun void ((int) (float) (struct what *)))
+   (walk-type '(fn ((int) (float) (* struct what)) void)))
+
+  (test
+   '(%fun void ((int) (%array (float)) (struct what *)))
+   (walk-type '(fn ((int) (¤ float) (* struct what)) void)))
+
+;;; Variable defs
+  (test
+   '(%var (%array (float) 8) a)
+   (walk-var '(var a (¤ float 8))))
+
+  (test
+   '(%var (int *) a (& n))
+   (walk-var '(var a (* int) (& n))))
+
+  (test
+   '(%var (const int *) a (& n))
+   (walk-var '(var a (* const int) (& n))))
+
+  (test
+   '(%var (struct suc) s)
+   (walk-var '(var s (struct suc))))
+
+  (test
+   '(%var (struct suc) s (hoge piyo))
+   (walk-var '(var s (struct suc) (hoge piyo))))
+
+  (test
+   '(%var (struct suc *) s (hoge piyo))
+   (walk-var '(var s (* struct suc) (hoge piyo))))
+
+;;; Fn defs
+  (test
+   '(%fun void puk ((int) (%array (float) 8)))
+   (walk-fn-def '(fn puk ((int) (¤ float 8)) void)))
+
+  (test
+   '(%fun int main ((int argc) ((%array (const char)) argv))
+          (return 0))
+   (walk-fn-def
+    '(fn main ((argc int) (argv (¤ const char))) int
+         (return 0))))
+  (test
+   '(%fun int quxu (((struct piq *) bar))
+          (return 0))
+   (walk-fn-def
+    '(fn quxu ((bar (* struct piq))) int
+         (return 0))))
+
+  (test
+   '(%fun int quxu (((struct piq *) bar) ((%array (struct tt *)) ploop))
+          (return 0))
+   (walk-fn-def
+    '(fn quxu ((bar (* struct piq)) (ploop (¤ * struct tt))) int
+         (return 0))))
+
+  ;; Structs
+  (test
+   '(struct no_kebab ((int a) (float f)))
+   (walk-struct '(struct no-kebab ((a int) (f float)))))
+
+  (test
+   '(struct mega_kebab ((int a)
+                        ((struct ((int year) (int month) (int day))) dob)
+                        ((%fun int ((int) (%array (int)))) min)))
+   (walk-struct '(struct mega-kebab
+                         ((a int)
+                          (dob (struct ((year int)
+                                        (month int)
+                                        (day int))))
+                          (min (fn ((int) (¤ int)) bool)))))))