Adding DIImportedModules to DIScopes.

This is just the basic groundwork for supporting DW_TAG_imported_module but I
wanted to commit this before pushing support further into Clang or LLVM so that
this rather churny change is isolated from the rest of the work. The major
churn here is obviously adding another field (within the common DIScope prefix)
to all DIScopes (files, classes, namespaces, lexical scopes, etc). This should
be the last big churny change needed for DW_TAG_imported_module/using directive
support/PR14606.

llvm-svn: 178099
diff --git a/llvm/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll b/llvm/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
index 39a026c..43b5e4a 100644
--- a/llvm/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
+++ b/llvm/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
@@ -42,26 +42,26 @@
 }
 
 !llvm.dbg.cu = !{!0, !10}
-!0 = metadata !{i32 786449, metadata !23, i32 12, metadata !"clang version 3.3", i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !3, metadata !1, metadata !""} ; [ DW_TAG_compile_unit ]
+!0 = metadata !{i32 786449, metadata !23, null, i32 12, metadata !"clang version 3.3", i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !3, metadata !1, metadata !""} ; [ DW_TAG_compile_unit ]
 !1 = metadata !{metadata !2}
 !2 = metadata !{i32 0}
 !3 = metadata !{metadata !5}
-!5 = metadata !{i32 786478, metadata !23, metadata !"test", metadata !"test", metadata !"", metadata !6, i32 2, metadata !7, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 (i32)* @test, null, null, metadata !1, i32 3} ; [ DW_TAG_subprogram ] [line 2] [def] [scope 3] [test]
-!6 = metadata !{i32 786473, metadata !23} ; [ DW_TAG_file_type ]
-!7 = metadata !{i32 786453, i32 0, metadata !"", i32 0, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !8, i32 0, i32 0} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!5 = metadata !{i32 786478, metadata !23, null, metadata !"test", metadata !"test", metadata !"", metadata !6, i32 2, metadata !7, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 (i32)* @test, null, null, metadata !1, i32 3} ; [ DW_TAG_subprogram ] [line 2] [def] [scope 3] [test]
+!6 = metadata !{i32 786473, metadata !23, null} ; [ DW_TAG_file_type ]
+!7 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !8, i32 0, i32 0} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
 !8 = metadata !{metadata !9, metadata !9}
-!9 = metadata !{i32 786468, null, metadata !"int", null, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
-!10 = metadata !{i32 786449, metadata !24, i32 12, metadata !"clang version 3.3 (trunk 172862)", i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !11, metadata !1, metadata !""} ; [ DW_TAG_compile_unit ]
+!9 = metadata !{i32 786468, null, null, metadata !"int", null, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!10 = metadata !{i32 786449, metadata !24, null, i32 12, metadata !"clang version 3.3 (trunk 172862)", i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !11, metadata !1, metadata !""} ; [ DW_TAG_compile_unit ]
 !11 = metadata !{metadata !13}
-!13 = metadata !{i32 786478, metadata !24, metadata !"fn", metadata !"fn", metadata !"", metadata !14, i32 1, metadata !7, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 (i32)* @fn, null, null, metadata !1, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [fn]
-!14 = metadata !{i32 786473, metadata !24} ; [ DW_TAG_file_type ]
+!13 = metadata !{i32 786478, metadata !24, null, metadata !"fn", metadata !"fn", metadata !"", metadata !14, i32 1, metadata !7, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 (i32)* @fn, null, null, metadata !1, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [fn]
+!14 = metadata !{i32 786473, metadata !24, null} ; [ DW_TAG_file_type ]
 !15 = metadata !{i32 786689, metadata !5, metadata !"a", metadata !6, i32 16777218, metadata !9, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [a] [line 2]
 !16 = metadata !{i32 2, i32 0, metadata !5, null}
 !17 = metadata !{i32 4, i32 0, metadata !18, null}
-!18 = metadata !{i32 786443, metadata !23, metadata !5, i32 3, i32 0, i32 0} ; [ DW_TAG_lexical_block ]
+!18 = metadata !{i32 786443, metadata !23, null, metadata !5, i32 3, i32 0, i32 0} ; [ DW_TAG_lexical_block ]
 !19 = metadata !{i32 786689, metadata !13, metadata !"a", metadata !14, i32 16777217, metadata !9, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [a] [line 1]
 !20 = metadata !{i32 1, i32 0, metadata !13, null}
 !21 = metadata !{i32 2, i32 0, metadata !22, null}
-!22 = metadata !{i32 786443, metadata !24, metadata !13, i32 1, i32 0, i32 0} ; [ DW_TAG_lexical_block ]
+!22 = metadata !{i32 786443, metadata !24, null, metadata !13, i32 1, i32 0, i32 0} ; [ DW_TAG_lexical_block ]
 !23 = metadata !{metadata !"simple.c", metadata !"/private/tmp"}
 !24 = metadata !{metadata !"simple2.c", metadata !"/private/tmp"}