Refactor the DIFile (2nd) parameter to DITypes to be an MDNode reference to a raw directory/file pair

This makes DIType's first non-tag parameter the same as DIFile's, allowing them
to both share the common implementation of getFilename/getDirectory in DIScope.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177467 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/DebugInfo/X86/empty-array.ll b/test/DebugInfo/X86/empty-array.ll
index 624e9ed..7a02334 100644
--- a/test/DebugInfo/X86/empty-array.ll
+++ b/test/DebugInfo/X86/empty-array.ll
@@ -29,9 +29,9 @@
 !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]
 !6 = metadata !{i32 786473, metadata !20} ; [ DW_TAG_file_type ]
-!7 = metadata !{i32 786434, metadata !6, null, metadata !"A", i32 1, i64 0, i64 32, i32 0, i32 0, null, metadata !8, i32 0, null, null} ; [ DW_TAG_class_type ] [A] [line 1, size 0, align 32, offset 0] [from ]
+!7 = metadata !{i32 786434, metadata !20, null, metadata !"A", i32 1, i64 0, i64 32, i32 0, i32 0, null, metadata !8, i32 0, null, null} ; [ DW_TAG_class_type ] [A] [line 1, size 0, align 32, offset 0] [from ]
 !8 = metadata !{metadata !9, metadata !14}
-!9 = metadata !{i32 786445, metadata !6, metadata !7, metadata !"x", i32 1, i64 0, i64 0, i64 0, i32 1, metadata !10} ; [ DW_TAG_member ] [x] [line 1, size 0, align 0, offset 0] [private] [from ]
+!9 = metadata !{i32 786445, metadata !20, metadata !7, metadata !"x", i32 1, i64 0, i64 0, i64 0, i32 1, metadata !10} ; [ DW_TAG_member ] [x] [line 1, size 0, align 0, offset 0] [private] [from ]
 !10 = metadata !{i32 786433, null, null, metadata !"", i32 0, i64 0, i64 32, i32 0, i32 0, metadata !11, metadata !12, i32 0, i32 0} ; [ DW_TAG_array_type ] [line 0, size 0, align 32, offset 0] [from int]
 !11 = metadata !{i32 786468, null, null, metadata !"int", 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]
 !12 = metadata !{metadata !13}