Introduce NetBSD support

Current FreeBSD and NetBSD code is compatible.


git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@260001 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/AddressSpace.hpp b/src/AddressSpace.hpp
index 73013c7..da1b6a4 100644
--- a/src/AddressSpace.hpp
+++ b/src/AddressSpace.hpp
@@ -35,7 +35,7 @@
 #include "Registers.hpp"
 
 #if _LIBUNWIND_ARM_EHABI
-#if defined(__FreeBSD__)
+#if defined(__FreeBSD__) || defined(__NetBSD__)
 
 typedef void *_Unwind_Ptr;
 
@@ -61,7 +61,8 @@
 #endif // !defined(_LIBUNWIND_IS_BAREMETAL)
 #endif // _LIBUNWIND_ARM_EHABI
 
-#if defined(__CloudABI__) || defined(__FreeBSD__) || defined(__linux__)
+#if defined(__CloudABI__) || defined(__FreeBSD__) || defined(__linux__) ||	\
+    defined(__NetBSD__)
 #if _LIBUNWIND_SUPPORT_DWARF_UNWIND && _LIBUNWIND_SUPPORT_DWARF_INDEX
 #include <link.h>
 // Macro for machine-independent access to the ELF program headers. This