[DynInst_API:] COMMIT [testsuite]: fix c++ test failure on Windows

[Xiaozhu Meng <xmeng@xxxxxxxxxxx>]

Our c++ test failures on Windows were caused by incompatible ABI call
conventions. When we insert a function call to a cpp funtion, Dyninst
generated code  to set parameters according to __stdcall while the
callee was expecting __thiscall style parameter setting.

A real solution should be for Dyninst to generate appropriate code
according to which ABI the callee is expecting. Currently, we force
these cpp functions to also use __stdcall.