libunwind: fix register numbering on OpenBSD/i386 (again)

[Patrick Wildt]

Hi,

during the libunwind update to 6.0 we lost a particular patchset that
fixes register numbering for OpenBSD/i386, thus breaking exception
handling on that platform.  Looks like no one noticed until now.

ok?

Patrick

diff --git a/lib/libunwind/include/libunwind.h 
b/lib/libunwind/include/libunwind.h
index 29cf62e4335..4ff0c01b4e2 100644
--- a/lib/libunwind/include/libunwind.h
+++ b/lib/libunwind/include/libunwind.h
@@ -164,8 +164,13 @@ enum {
   UNW_X86_ECX = 1,
   UNW_X86_EDX = 2,
   UNW_X86_EBX = 3,
+#ifdef __OpenBSD__
+  UNW_X86_ESP = 4,
+  UNW_X86_EBP = 5,
+#else
   UNW_X86_EBP = 4,
   UNW_X86_ESP = 5,
+#endif
   UNW_X86_ESI = 6,
   UNW_X86_EDI = 7
 };