Disable C++ exceptions in the kernel driver

CMake puts /EHsc in CMAKE_CXX_FLAGS by default. The /GR it also adds
was already being stripped here, but /EHsc was not, and /kernel does
not turn exception handling off by itself -- so the driver compiled
with _CPPUNWIND defined and every STL and PawnPP throwing path live.
Nothing throws today, so the link stayed clean, but noexcept violations
lowered to __std_terminate and one throwing instantiation would have
pulled in _CxxThrowException/__CxxFrameHandler4, which do not exist in
kernel mode.

Strip it the same way /GR is stripped, and put it back on PawnIOLib and
PawnIOUtil, which are user mode and where PawnIOUtil genuinely relies
on throwing STL. The driver now compiles with no /EH option at all.