Properly enable -freorder-blocks-and-partition on 64-bit Windows

Properly enable -freorder-blocks-and-partition on 64-bit Windows

The PR uncovered that -freorder-blocks-and-partition was working by accident
on 64-bit Windows, i.e. the middle-end was supposed to disable it with SEH.
After the change installed on mainline, the middle-end properly disables it,
which is too bad since a significant amount of work went into it for SEH.

gcc/
	PR target/103465
	* coretypes.h (unwind_info_type): Swap UI_SEH and UI_TARGET.