add vector-copy and vector-copy!
check vector index out of range
wipe reallocated cv_tbl
[bugfix] fix crash on deeply nested lambdas
add vector-append
change -O option depending on make rule
when restoring continuation sp and ci must be re-allocated
add global exception handler stack
[bugfix] after save_cont any local variable must not be modified!

If save_cont returns a cont object, a local variable will receive the
object and the machine stack state will have just been changed then.
To avoid that, we need set cont object to the local before the machine
stack is copied.
add pic_errorf
[bugfix] local variables should be initialized before copied to env object
initial exception handling support