Changes in 3.86
chain.c32: fix chainloading the MBR of a hard disk (broken in 3.85).
mboot.c32: report the boot loader name in the information structure.
com32: set argv in a com32 module.
core: add a workaround for a bug in Xen HVM older than version 3.3: disable halt on those platforms.
Fix problems where certain operations in com32 modules would cause the core to believe the system was idle.
MEMDISK: fix MBR detection when used with a DOSEMU header or an offset.
MEMDISK: generate the mBFT checksum correctly.