* i386-win32 setjmp and longjmp: if SEH support is enabled, save/restore head of exception registration chain. Without this, a longjmp out of a function with exception frame(s) will leave these exception frames below ESP, which will fail integrity checks in OS and cause process termination if an exception occurs later on (or they may be overwritten by subsequent operations on stack and, again, cause undesired results).
* Additionally, use a branchless sequence to fix up result of longjmp.


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@26238 3ad0048d-3df7-0310-abae-a5850022a9f2