only mainthread can use sleep builtin function

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>
remove some unused builtin function

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>
fix ktap exit issue finally

ktap have exit issue at long time ago, ktapvm exit in kernel,
not return to usersapce, the problem is there have some cleanup
work need to do after tracing, like remove kprobe/uprobe event file,
etc...

Now the issued is fixed.

One rule about ktap thread exit: use injected OP_EXIT instruction
to disable continue execution after kp_exit is called,

What kp_exit doing is very simple now, it just set a flag, and set
next execution instruction to OP_EXIT, ktapvm bytecode engine find
the instruction is OP_EXIT, then it return to upper layer, finally
goto kp_final_exit, kp_final_exit cleanup all resources, then
return to userspace.

Because of OP_EXIT, there don't need any return value checking for
library function calling, this will boost performance a little.

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>
fix cannot parse event filter include ksoftirqd/0

Currently ktap cannot parse event filter like 'prev_comm == ksoftirqd/0',
this patch fix it.

Note this patch will make uprobe eventdef cannot work, fix it later.

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>