Revert "Revert "PR14606: debug info imported_module support""

This reverts commit r179840 with a fix to test/DebugInfo/two-cus-from-same-file.ll

I'm not sure why that test only failed on ARM & MIPS and not X86 Linux, even
though the debug info was clearly invalid on all of them, but this ought to fix
it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179996 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/DebugInfo/X86/empty-array.ll b/test/DebugInfo/X86/empty-array.ll
index ace1156..1f46281 100644
--- a/test/DebugInfo/X86/empty-array.ll
+++ b/test/DebugInfo/X86/empty-array.ll
@@ -24,7 +24,7 @@
 
 !llvm.dbg.cu = !{!0}
 
-!0 = metadata !{i32 786449, metadata !20, i32 4, metadata !"clang version 3.3 (trunk 169136)", i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !1, metadata !3, metadata !""} ; [ DW_TAG_compile_unit ] [/Volumes/Sandbox/llvm/t.cpp] [DW_LANG_C_plus_plus]
+!0 = metadata !{i32 786449, metadata !20, i32 4, metadata !"clang version 3.3 (trunk 169136)", i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !1, metadata !3,  metadata !3, metadata !""} ; [ DW_TAG_compile_unit ] [/Volumes/Sandbox/llvm/t.cpp] [DW_LANG_C_plus_plus]
 !1 = metadata !{i32 0}
 !3 = metadata !{metadata !5}
 !5 = metadata !{i32 786484, i32 0, null, metadata !"a", metadata !"a", metadata !"", metadata !6, i32 1, metadata !7, i32 0, i32 1, %class.A* @a, null} ; [ DW_TAG_variable ] [a] [line 1] [def]