[USETUP]

[USETUP]
- bootsup.c/.h, usetup.c: Save the old MBR sector in the system partition (this makes easier to restore the old one).
- fslist.c/.h, usetup.h: Fix header inclusion order.
- partlist.c/.h, usetup.c: On BIOS-PC architectures, the system partition can be formatted in any FS as long as it is the active partition (on the contrary, on architectures where such system partition is required, it is formatted in FAT). We currently do not have write support for all FSes out there (apart for FAT until now), so do a "clever" "trick" to work around this problem: on initialized disks, find the active partition and check its FS. If we support write access to this FS then we're OK, otherwise we change the (active) system partition for the one on which we are going to install ReactOS (which is, by construction, formatted with a FS on which we support write access).
The MBR (resp. the VBR) of the disk (resp. of the system partition) are always saved into files, making easy for people to boot on them (using FreeLdr) or restoring them.

CORE-10898

svn path=/trunk/; revision=70837