let OP_RET take an argument
add coarity register to the VM
[bugfix] handle 1-coarity native function
VM end state shows info based on the position the VM entered
show invalid application callee
[refactor] proceed return values from C functions in OP_RET block
ci->retc is set to 1 by default
reset ci->retc when pic_receive is called
adjust stack pointer to the next to the initial position after calling function
don't emit debug message into stderr
don't reset retc in pic_receive
compile values in tail position
support call-with-values in VM level
Merge branch 'native-mv'. fix #16