PSEH3 exception record is below esp in exception handler

What happens is if you use the stack too much, the exception record will be overwritten.
Real world case where this happens is IoCreateFile, which calls ExFreePool in the exception handler, and that uses a lot of stack. Result is that the subsequent call to _SEH2_GetExceptionCode may return the wrong value (e.g. 0 which can lead to a lot of confusion).

pseh3-stackframe-test.patch – test case added to pseh2_test
psehtest.pp.c – preprocessed output, with some formatting applied
psehtest.c.asm – assembly output

The test case currently crashes:
C:\ROS\reactos\output-MinGW-i386\reactos>modules\rostests\tests\pseh2\pseh2_test.exe
psehtest.c:2599: unhandled exception C0000005 thrown from 004078BA

With the printf uncommented and the array fill disabled, the output shows the situation (esp > exception record):
0028F6D8, 0028FA10
psehtest.c:2897: Test failed: test_PSEH3_bug2 failed
pseh2_syntax: 104 tests executed (0 marked as todo, 1 failure), 0 skipped.

cc thephysicist, zefklop