This change is adding DWARF (CFI) unwind information to the hand-written assembly of the `__wine_syscall_dispatcher` function. This enables unwinding through the dispatcher from the Linux stack into (and through) the Windows stack.
The general idea is that the `syscall_frame` struct contains the content of the callee-save registers before the function call (in particular the stack pointer and the return address). At any point of the execution, we have a pointer into the `syscall_frame` in $ebx, $ecx, $ebp, or $esp.
For the CFI codes the general idea is that we are defining the computations of the callee-save registers based on the `syscall_frame` using DWARF’s `breg` instruction, rather than relative to CFA.
cc/ @florian-kuebler
-- v2: ntdll: Add CFI unwind info to __wine_syscall_dispatcher (i386).