[fpc-pascal] Firebird embedded supported on Windows 64 by SEH patch

[Reinier Olislagers]

Sergei Gorelkin enabled Win64 SEH support in trunk r23732:

* Make Win64 SEH support enabled by default. If necessary to disable,
compiler should be cycled with OPT=-dDISABLE_WIN64_SEH. Mantis #24012.

Seems this fixes issues on Win64 with e.g. embedded Firebird dlls, and
I'm sure many other DLLs.

Thanks a lot, Sergei!

Regards,
Reinier