minor probelm in current.stp

[Wenji Huang]

Hi,

 Regarding to testsuite/systemtap/current.stp, there are probe like

    module("*").function("*interrupt*").call,
    module("*").function("*interrupt*").return

 In rare case, no module/no such function in module will result in 
current.stp failing.

 Also other test scripts.
    buildok/four.stp
    buildok/twentyfive.stp
    semok/twelve.stp

 are related to kernel config. They fail when the modules are built-in.

 So I think we had better make them optional or create a little 
complicated exp file to less FAIL from kernel config.

 If no objection, I will do that.

Thanks.
Wenji