Modify handling of serialize:dir parameter to make it more useful.

Modify handling of serialize:dir parameter to make it more useful.

Move global checkpoint-related functions and vars into Checkpoint class (as statics).

arch/alpha/pseudo_inst.cc:
dev/disk_image.cc:
    Move global checkpoint-related functions and vars
    into Checkpoint class (as statics).
sim/serialize.cc:
    Move global checkpoint-related functions and vars
    into Checkpoint class (as statics).

    Checkpoint constructor now takes checkpoint directory name instead
    of file name.

    Make serialize:dir parameter actually set checkpoint directory name
    instead of directory in which checkpoint directory is created.  If
    the value contains a '%', the curTick value is sprintf'd into the
    format to create the directory name.  The default is backwards compatible
    with the old fixed name ("m5.%012d").
sim/serialize.hh:
    Move global checkpoint-related functions and vars
    into Checkpoint class (as statics).

    Checkpoint constructor now takes checkpoint directory name instead
    of file name.

--HG--
extra : convert_revision : d0aa87b62911f405a4f5811271b9e6351fdd9fe4