DebugInfo: Fix bad debug info for compile units and types

Fix debug info in these tests, which started failing with a WIP patch to
verify compile units and types.  The problems look like they were all
caused by bitrot.  They fell into these categories:

  - Using `!{i32 0}` instead of `!{}`.
  - Using `!{null}` instead of `!{}`.
  - Using `!MDExpression()` instead of `!{}`.
  - Using `!8` instead of `!{!8}`.
  - `file:` references that pointed at `MDCompileUnit`s instead of the
    same `MDFile` as the compile unit.
  - `file:` references that were numerically off-by-one or (off-by-ten).

llvm-svn: 233415
diff --git a/llvm/test/DebugInfo/X86/dbg-const-int.ll b/llvm/test/DebugInfo/X86/dbg-const-int.ll
index 8aa4e1c..abe4e94 100644
--- a/llvm/test/DebugInfo/X86/dbg-const-int.ll
+++ b/llvm/test/DebugInfo/X86/dbg-const-int.ll
@@ -35,5 +35,5 @@
 !11 = !{!1}
 !12 = !{!6}
 !13 = !MDFile(filename: "a.c", directory: "/private/tmp")
-!14 = !{i32 0}
+!14 = !{}
 !15 = !{i32 1, !"Debug Info Version", i32 3}