user: Create pager to create normal user thread

Pager uses 'thread_pool' table to record and manage
the resource usage for each user thread in app.
ktimer: Free ktimer event when ktimer event schedule fails.
ipc: Ipc error handling

Create ipc error handler and set unsuccessful bit
in ipc tag when ipc fails.
ipc : Add timeout handling for send and receive ipc

Use ktimer event for ipc timeout.  If ipc does not complete before
this ktimer event, set this ipc thread running with timeout error
message.
ktimer: Fix delta recalculation in ktimer event

Recalculate delta only for next event of current scheduled event.
The delta of later events should not be modified by new scheduled
event.
ipc: do ipc immediately when receiver do ipc and sender has waited for this
user: Remove unused user space code

Pager now is the standard and unified interface for
resource management in user space.  Some user code is
obsolete and no longer needed anymore.
Merge pull request #106 from georgekang/master

implement pager as standard resource management in user space