Split out filename & directory from DIFile to start generalizing over DIScopes

This is the first step to making all DIScopes have a common metadata prefix (so
that things (using directives, for example) that can appear in any scope can be
added to that common prefix). DIFile is itself a DIScope so the common prefix
of all DIScopes cannot be a DIFile - instead it's the raw filename/directory
name pair.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177239 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/DebugInfo/two-cus-from-same-file.ll b/test/DebugInfo/two-cus-from-same-file.ll
index af1c581..c751713 100644
--- a/test/DebugInfo/two-cus-from-same-file.ll
+++ b/test/DebugInfo/two-cus-from-same-file.ll
@@ -36,7 +36,7 @@
 !1 = metadata !{i32 0}
 !3 = metadata !{metadata !5}
 !5 = metadata !{i32 786478, i32 0, metadata !6, metadata !"foo", metadata !"foo", metadata !"", metadata !6, i32 5, metadata !7, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 true, void ()* @foo, null, null, metadata !1, i32 5} ; [ DW_TAG_subprogram ]
-!6 = metadata !{i32 786473, metadata !"foo.c", metadata !"/tmp", null} ; [ DW_TAG_file_type ]
+!6 = metadata !{i32 786473, metadata !32} ; [ 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 ]
 !8 = metadata !{null}
 !9 = metadata !{i32 786449, i32 0, i32 12, metadata !6, metadata !"clang version 3.2 (trunk 156513)", i1 true, metadata !"", i32 0, metadata !1, metadata !1, metadata !10, metadata !1, metadata !""} ; [ DW_TAG_compile_unit ]
@@ -61,6 +61,7 @@
 !29 = metadata !{i32 786443, metadata !12, i32 11, i32 34, metadata !6, i32 0} ; [ DW_TAG_lexical_block ]
 !30 = metadata !{i32 13, i32 3, metadata !29, null}
 !31 = metadata !{i32 14, i32 3, metadata !29, null}
+!32 = metadata !{metadata !"foo.c", metadata !"/tmp"}
 
 ; This test is simple to be cross platform (many targets don't yet have
 ; sufficiently good DWARF emission and/or dumping)