Fixed loss of setting of the RB_BOOTINFO flag in rev.1.43. Fixed wrong

Fixed loss of setting of the RB_BOOTINFO flag in rev.1.43.  Fixed wrong
comment about this flag in rev.1.61.  It is not historical like the
comment said; it is the flag that says that most of what is laboriously
put in the bootinfo struct is actually there.  Newer kernels were
bootable by even the broken boot2 without losing anything except the
symbol table, but older kernels need at least the memory sizes.

Restoring the "|" with RB_BOOTINFO that was lost in rev.1.43 costs 5
bytes.  The fix can be done in only 4 bytes by fixing some code that
was removed in rev.1.61 (put RB_BOOTINFO back in in the initial value
of "opts" and fix RBX_MASK to not clobber it.)