The unwind info is now printed from unwind.c.

%gs is not set until call_init_thunk().
Also, adjust other TEB accesses to be consistent with the surrounding
functions.

Fixes a crash on macOS introduced by 7ae488a2
("ntdll: Don't hardcode xstate size in syscall frame.")

MSI_RecordGetIStream adds a reference to the stream. This
reference should be negated as we are done setting the stream.
Signed-off-by: David Kahurani <k.kahurani@gmail.com>