modularize sex

Also rename macros to sex-macros, module-system to sex-modules for
clarity, uniformity, and to avoid name clashes with Chicken's
units/modules named "macros" and "modules"

utils.macros.scm

@@ -1,17 +1 @@
 (import (chicken process-context))
-
-(define-syntax prog1
-  (syntax-rules ()
-    ((prog1 form . forms)
-     (let ((res form))
-       (begin . forms)
-       res))))
-
-(define-syntax with-directory
-  (syntax-rules ()
-    ((with-directory path form . forms)
-     (let ((current-dir (current-directory)))
-       (set-working-directory path)
-       (prog1
-        (begin form . forms)
-        (change-directory current-dir))))))