core: Move reader and posix functions from mes.c

* mes.c (getchar, ungetchar, peekchar, peek_byte, read_byte,
  unread_byte, write_byte, read_input_file_env_, read_input_file_env):
  Remove.
* posix.c (getchar, ungetchar, peekchar, peek_byte, read_byte,
  unread_byte, write_byte): Move from mes.c.
* reader (read_input_file_env_, read_input_file_env): Move from mes.c.

mes.c

@@ -787,59 +787,6 @@ vector_to_list (SCM v)
   return x;
 }
 
-FILE *g_stdin;
-int
-getchar ()
-{
-  return getc (g_stdin);
-}
-
-int
-ungetchar (int c)
-{
-  return ungetc (c, g_stdin);
-}
-
-int
-peekchar ()
-{
-  int c = getchar ();
-  ungetchar (c);
-  return c;
-}
-
-SCM
-peek_byte ()
-{
-  return MAKE_NUMBER (peekchar ());
-}
-
-SCM
-read_byte ()
-{
-  return MAKE_NUMBER (getchar ());
-}
-
-SCM
-unread_byte (SCM i)
-{
-  ungetchar (VALUE (i));
-  return i;
-}
-
-SCM
-write_byte (SCM x) ///((arity . n))
-{
-  SCM c = car (x);
-  SCM p = cdr (x);
-  int fd = 1;
-  if (TYPE (p) == PAIR && TYPE (car (p)) == NUMBER) fd = VALUE (car (p));
-  FILE *f = fd == 1 ? stdout : stderr;
-  assert (TYPE (c) == NUMBER || TYPE (c) == CHAR);
-  fputc (VALUE (c), f);
-  return c;
-}
-
 void
 make_tmps (scm* cells)
 {
@@ -1077,22 +1024,7 @@ lookup_macro (SCM x, SCM a)
   return cell_f;
 }
 
-SCM
+FILE *g_stdin;
-read_input_file_env_ (SCM e, SCM a)
-{
-  if (e == cell_nil) return e;
-  return cons (e, read_input_file_env_ (read_env (a), a));
-}
-
-SCM
-read_input_file_env (SCM a)
-{
-  r0 = a;
-  if (assq_ref_cache (cell_symbol_read_input_file, r0) != cell_undefined)
-    return apply_env (cell_symbol_read_input_file, cell_nil, r0);
-  return read_input_file_env_ (read_env (r0), r0);
-}
-
 SCM
 load_env (SCM a) ///((internal))
 {

posix.c

@@ -20,6 +20,58 @@
 
 #include <fcntl.h>
 
+int
+getchar ()
+{
+  return getc (g_stdin);
+}
+
+int
+ungetchar (int c)
+{
+  return ungetc (c, g_stdin);
+}
+
+int
+peekchar ()
+{
+  int c = getchar ();
+  ungetchar (c);
+  return c;
+}
+
+SCM
+peek_byte ()
+{
+  return MAKE_NUMBER (peekchar ());
+}
+
+SCM
+read_byte ()
+{
+  return MAKE_NUMBER (getchar ());
+}
+
+SCM
+unread_byte (SCM i)
+{
+  ungetchar (VALUE (i));
+  return i;
+}
+
+SCM
+write_byte (SCM x) ///((arity . n))
+{
+  SCM c = car (x);
+  SCM p = cdr (x);
+  int fd = 1;
+  if (TYPE (p) == PAIR && TYPE (car (p)) == NUMBER) fd = VALUE (car (p));
+  FILE *f = fd == 1 ? stdout : stderr;
+  assert (TYPE (c) == NUMBER || TYPE (c) == CHAR);
+  fputc (VALUE (c), f);
+  return c;
+}
+
 SCM
 stderr_ (SCM x)
 {

reader.c

@@ -18,6 +18,23 @@
  * along with Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+
+SCM
+read_input_file_env_ (SCM e, SCM a)
+{
+  if (e == cell_nil) return e;
+  return cons (e, read_input_file_env_ (read_env (a), a));
+}
+
+SCM
+read_input_file_env (SCM a)
+{
+  r0 = a;
+  if (assq_ref_cache (cell_symbol_read_input_file, r0) != cell_undefined)
+    return apply_env (cell_symbol_read_input_file, cell_nil, r0);
+  return read_input_file_env_ (read_env (r0), r0);
+}
+
 int
 read_line_comment (int c)
 {