Fix another -freorder-blocks-and-partition glitch with Windows SEH

Since GCC 8, the -freorder-blocks-and-partition pass can split a function
into hot and cold parts, thus generating 2 FDEs for a single function in
DWARF for exception purposes and doing an equivalent trick for Windows SEH.

Now the Windows system unwinder does not support arbitrarily large frames
and there is even a hard limit on the encoding of the CFI, which changes
the stack allocation strategy when it is topped and which must be reflected
everywhere.

gcc/
	* config/i386/winnt.c (i386_pe_seh_cold_init): Properly deal with
	frames larger than the SEH maximum frame size.
gcc/testsuite/
	* gnat.dg/opt92.adb: New test.