Fix the regkey search bug when XARMcreate() causes an error at enlistment
in DTC.
Register the XA DLL on installation.
MSDTC runs in 64bit mode on 64bit machines and 32bit mode on 32bit machines.
We had better register the XA DLL on installation.
More improvement on MSDTC enlistment.
Use xaopt connection string option so as to ,,,