Add support for Clang UBSan and enable it by default.
Add support for Clang UBSan and enable it by default.

twoporeguys/librpc,twoporeguys/librpc,twoporeguys/librpc,twoporeguys/librpc,twoporeguys/librpc,twoporeguys/librpc,twoporeguys/librpc,twoporeguys/librpc