Fixes for compiler __try/__except support
This change allows building with compiler exception support enabled (-DUSE_COMPILER_EXCEPTIONS) on non-i386 targets.
On i386, _except_handler3 needs to be available. While we provide it as an import from the msvcrt DLLs, that's not sufficient for modules like
kernel32. Making this work would likely require moving _except_handler3 to winecrt0.
In practice, this fixes the build with Clang, although the resulting binaries do not appear to be fully correct yet. Further investigation is needed, likely on the LLVM side.