Clonezilla (64-bit)

What's new in this version:

- The underlying GNU/Linux operating system was upgraded. This release is based on the Debian Sid repository (as of 2020/Jun/30).
- Linux kernel was updated to 5.7.6-1
- ocs-iso, ocs-live-dev: sync syslinux-related files when copying syslinux exec files
- When creating recovery iso/zip file, if it's in Clonezilla live environment, we have those syslinux files. Use that first so the version mismatch can be avoided
- Move grub-header.cfg from bootx64.efi to grub.cfg so that it's more flexible
- To avoid conflict with the patch of grub in CentOS/Fedora, for GRUB EFI NB MAC/IP config style, the netboot file is now like grub.cfg-drbl-00:50:56:01:01:01 and grub.cfg-drbl-192.168.177.2 not grub.cfg-01-* anymore.
- Add xen-tools
- Partclone was updated to 0.3.14. The codes about xfs was updated to be 4.20.0
- Package exfat-fuse was removed since the kernel has module for that
- A better mechanism to deal with linuxefi/initrdefi or linux/initrd in the grub config was added