This changes the budget/remaining fields in scheduling contexts
to contain timer ticks, not number of abstract sel4ticks.
seL4_SchedControl_Configure now takes microseconds, not ticks.
This commit is plat-independant - the platform and arch specific
timer code follows in later commits.
This is the first part of the seL4 MCS. This commit:
* adds a scheduling context object. Threads without scheduling
context objects cannot be scheduled.
* replaces tcbTimeSlice with the scheduling context object
* adds seL4_SchedControl caps for each core
* adds seL4_SchedControl_Configure which allows users to configure
amount of ticks a scheduling context has, and set a core for the
scheduling context.
* adds seL4_SchedContext_Bind, Unbind and UnbindObject, which allows
a tcb to be bound to a scheduling context.
