mini-mes: Merge with mes.c: lib.c, math.c, posix.c.

mini-mes: Merge with mes.c: lib.c, math.c, posix.c.

* mes.c: Include math.c after posix.c.
  (assert_defined, check_formals, check_apply, load_env,
  bload_env): Move from lib.c
* scaffold/mini-mes.c: Include mini-lib.h, lib.c., mini-math.h,
  math.c, mini-posix.h, posix.c.
  (greater_p, less_p, is_p, minus, plus, divide, modulo, multiply,
  logior, ash): Remove.
  (ungetchar, peekchar, peek_byte, read_byte, write_byte,
  string_to_cstring, getenv_, open_input_file, current_input_port,
  set_current_input_port, force_output): Remove.
  (mes_builtins): include mini-lib.i, mini-lib.environment.i.
  mini-math.i, mini-math.environment.i mini-posix.i,
  mini-posix.environment.i.
* GNUmakefile (guile-mini-mes): Add dependencies.