terminal: weaken color argument order requirement

With this patch, the escape sequence decoder can handle a two-argument
'SGR' command with the attribute/color arguments in any order.

Fixes #690.
terminal: 'ED' command fix

Fixes #691.
L4Linux stability improvements

- search for alternative virtual address regions upwards, starting from
  the given start address, in the 'l4re_rm_attach()' and
  'Region_manager::reserve_range()' functions

- don't treat memory locations above 0x80000000 in l4linux's virtual
  address space as device memory

- align the start address of the vmalloc area according to the assumption
  in 'devicemaps_init()'

Fixes #414.