In the current behavior, include/ dirs in mrbgems are set to
core's compiler.include_paths.
And they are never set to mrbgem's include_paths.
It may cause some dangerous issues because it can change
mruby core's macros by mrbgems.

After this fix, include/ in a gem is used in the gem itself only.

Remove redundant substitutions.

"#{MRUBY_ROOT}/include" is set in Command::Compiler#initialize .

Add test for end-of-program marker.

Treat partial hook success '\n' to fix #2361 .

Ignore outfile check when `-c`(check syntax only) flag is enabled.

Now it will parse the #2361 code as:
```
module A
end
module B
end
```
instead of
```
module A
end module B
end
```

Add generator script to dependency so that it will regenerate C codes when it's modified.

various mruby-struct function changes

Release `mrb->atexit_stack` on `mrb_close`.

Fix compilation fail caused by GNU Readline and `ISPRINT`.
Also add missing `unsigned char` cast.

`ISSPACE` and `ISASCII` can be used instead.