Add x86_64 support.

(Logical change 1.249)
diff --git a/Makefile.am b/Makefile.am
index 6ae8a6a..695ddfc 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -6,6 +6,10 @@
 else
 if ARCH_X86
 include_HEADERS_tdep = include/libunwind-x86.h
+else
+if ARCH_X86_64
+include_HEADERS_tdep = include/libunwind-x86_64.h
+endif # ARCH_X86_64
 endif # ARCH_X86
 endif # ARCH_HPPA
 endif # ARCH_IA64
@@ -29,6 +33,9 @@
 	include/ia64/script.h						\
 	include/libunwind-hppa.h include/tdep-hppa.h			\
 	include/libunwind-x86.h include/tdep-x86.h			\
-	include/x86/dwarf-config.h
+	include/x86/dwarf-config.h					\
+	include/libunwind-x86_64.h include/tdep-x86_64.h		\
+	include/x86/dwarf-config.h					\
+	include/x86_64/dwarf-config.h
 
 DISTCLEANFILES = include/libunwind.h include/tdep.h