Debug info: refactor the first field of DICompileUnit to be a raw file/directory pair

This removes the DICompileUnit special case from DIScope.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177610 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/DebugInfo/X86/empty-and-one-elem-array.ll b/test/DebugInfo/X86/empty-and-one-elem-array.ll
index f90da4d..c01c581 100644
--- a/test/DebugInfo/X86/empty-and-one-elem-array.ll
+++ b/test/DebugInfo/X86/empty-and-one-elem-array.ll
@@ -59,7 +59,7 @@
 
 !llvm.dbg.cu = !{!0}
 
-!0 = metadata !{i32 786449, metadata !6, i32 12, metadata !"clang version 3.3 (trunk 169136)", i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !3, metadata !1, metadata !""} ; [ DW_TAG_compile_unit ] [/Volumes/Sandbox/llvm/test.c] [DW_LANG_C99]
+!0 = metadata !{i32 786449, metadata !32, i32 12, metadata !"clang version 3.3 (trunk 169136)", i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !3, metadata !1, metadata !""} ; [ DW_TAG_compile_unit ] [/Volumes/Sandbox/llvm/test.c] [DW_LANG_C99]
 !1 = metadata !{i32 0}
 !3 = metadata !{metadata !5}
 !5 = metadata !{i32 786478, i32 0, metadata !6, metadata !"func", metadata !"func", metadata !"", metadata !6, i32 11, metadata !7, i1 false, i1 true, i32 0, i32 0, null, i32 0, i1 false, i32 ()* @func, null, null, metadata !1, i32 11} ; [ DW_TAG_subprogram ] [line 11] [def] [func]