publish pic_defmacro as a public API

include/picrin.h

@@ -101,6 +101,7 @@ void pic_close(pic_state *);
 struct pic_proc *pic_get_proc(pic_state *);
 int pic_get_args(pic_state *, const char *, ...);
 void pic_defun(pic_state *, const char *, pic_func_t);
+void pic_defmacro(pic_state *, const char *, struct pic_proc *);
 
 pic_sym pic_intern_cstr(pic_state *, const char *);
 const char *pic_symbol_name(pic_state *, pic_sym);

src/macro.c

@@ -11,7 +11,7 @@
 
 #define FALLTHROUGH ((void)0)
 
-static void
+void
 pic_defmacro(pic_state *pic, const char *name, struct pic_proc *macro)
 {
   int idx;