IR: Make metadata typeless in assembly

Now that `Metadata` is typeless, reflect that in the assembly.  These
are the matching assembly changes for the metadata/value split in
r223802.

  - Only use the `metadata` type when referencing metadata from a call
    intrinsic -- i.e., only when it's used as a `Value`.

  - Stop pretending that `ValueAsMetadata` is wrapped in an `MDNode`
    when referencing it from call intrinsics.

So, assembly like this:

    define @foo(i32 %v) {
      call void @llvm.foo(metadata !{i32 %v}, metadata !0)
      call void @llvm.foo(metadata !{i32 7}, metadata !0)
      call void @llvm.foo(metadata !1, metadata !0)
      call void @llvm.foo(metadata !3, metadata !0)
      call void @llvm.foo(metadata !{metadata !3}, metadata !0)
      ret void, !bar !2
    }
    !0 = metadata !{metadata !2}
    !1 = metadata !{i32* @global}
    !2 = metadata !{metadata !3}
    !3 = metadata !{}

turns into this:

    define @foo(i32 %v) {
      call void @llvm.foo(metadata i32 %v, metadata !0)
      call void @llvm.foo(metadata i32 7, metadata !0)
      call void @llvm.foo(metadata i32* @global, metadata !0)
      call void @llvm.foo(metadata !3, metadata !0)
      call void @llvm.foo(metadata !{!3}, metadata !0)
      ret void, !bar !2
    }
    !0 = !{!2}
    !1 = !{i32* @global}
    !2 = !{!3}
    !3 = !{}

I wrote an upgrade script that handled almost all of the tests in llvm
and many of the tests in cfe (even handling many `CHECK` lines).  I've
attached it (or will attach it in a moment if you're speedy) to PR21532
to help everyone update their out-of-tree testcases.

This is part of PR21532.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224257 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/LoopStrengthReduce/AArch64/lsr-memset.ll

@@ -96,6 +96,6 @@ done:                                             ; preds = %while.cond, %while.
   ret i8* %dest
 }
 
-!0 = metadata !{metadata !"omnipotent char", metadata !1}
-!1 = metadata !{metadata !"Simple C/C++ TBAA"}
-!2 = metadata !{metadata !"long long", metadata !0}
+!0 = !{!"omnipotent char", !1}
+!1 = !{!"Simple C/C++ TBAA"}
+!2 = !{!"long long", !0}

test/Transforms/LoopStrengthReduce/pr12018.ll

@@ -16,7 +16,7 @@ for.body:                                         ; preds = %_ZN8nsTArray9Elemen
   %tmp = bitcast %struct.nsTArrayHeader* %add.ptr.i to %struct.nsTArray*
   %arrayidx = getelementptr inbounds %struct.nsTArray* %tmp, i32 %i.06
   %add = add nsw i32 %i.06, 1
-  call void @llvm.dbg.value(metadata !{%struct.nsTArray* %aValues}, i64 0, metadata !0, metadata !{}) nounwind
+  call void @llvm.dbg.value(metadata %struct.nsTArray* %aValues, i64 0, metadata !0, metadata !{}) nounwind
   br label %_ZN8nsTArray9ElementAtEi.exit
 
 _ZN8nsTArray9ElementAtEi.exit:                    ; preds = %for.body
@@ -35,4 +35,4 @@ declare %struct.nsTArrayHeader* @_ZN8nsTArray4Hdr2Ev()
 
 declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnone
 
-!0 = metadata !{metadata !"0x101"}                       ; [ DW_TAG_arg_variable ]
+!0 = !{!"0x101"}                       ; [ DW_TAG_arg_variable ]

test/Transforms/LoopStrengthReduce/pr18165.ll

@@ -77,12 +77,12 @@ attributes #2 = { nounwind optsize }
 
 !llvm.ident = !{!0}
 
-!0 = metadata !{metadata !"clang version 3.5 "}
-!1 = metadata !{metadata !2, metadata !3, i64 0}
-!2 = metadata !{metadata !"", metadata !3, i64 0, metadata !3, i64 4, metadata !3, i64 8}
-!3 = metadata !{metadata !"int", metadata !4, i64 0}
-!4 = metadata !{metadata !"omnipotent char", metadata !5, i64 0}
-!5 = metadata !{metadata !"Simple C/C++ TBAA"}
-!6 = metadata !{metadata !2, metadata !3, i64 8}
-!7 = metadata !{metadata !3, metadata !3, i64 0}
-!8 = metadata !{metadata !2, metadata !3, i64 4}
+!0 = !{!"clang version 3.5 "}
+!1 = !{!2, !3, i64 0}
+!2 = !{!"", !3, i64 0, !3, i64 4, !3, i64 8}
+!3 = !{!"int", !4, i64 0}
+!4 = !{!"omnipotent char", !5, i64 0}
+!5 = !{!"Simple C/C++ TBAA"}
+!6 = !{!2, !3, i64 8}
+!7 = !{!3, !3, i64 0}
+!8 = !{!2, !3, i64 4}