This uses BSON as savestate format, to allow external tools to parse it
(so that we can add proper test of the states). The BSON is not 100%
correct according to spec (no ordered keys) but can be parsed by most
libraries.
This fixes also a bug in the savestate palette color recalculation that
was wrongly overwritting the original palette (which could cause some
problems on some games).
Also fixes some potential issues by serializing some more stuff and
cleans up unused stuff.
Testing shows that states look good and there's only minor differences
in audio ticks, related to buffer sizes (since buffer flushes are
de-synced from video frames due to different frequency).
Add options to select whether to boot from BIOS (default is no, as it is
now) and whether to use the original bios or the builtin one (default is
auto, which tries to use the official but falls back to the builtin if
not found).
this also changes how direct sound channels are started and
sample step precision is increased to hopefully fix gbc + direct
channel desync that has been reported on the forums.
