IR: Move MDLocation into place

This commit moves `MDLocation`, finishing off PR21433.  There's an
accompanying clang commit for frontend testcases.  I'll attach the
testcase upgrade script I used to PR21433 to help out-of-tree
frontends/backends.

This changes the schema for `DebugLoc` and `DILocation` from:

    !{i32 3, i32 7, !7, !8}

to:

    !MDLocation(line: 3, column: 7, scope: !7, inlinedAt: !8)

Note that empty fields (line/column: 0 and inlinedAt: null) don't get
printed by the assembly writer.

llvm-svn: 226048
diff --git a/llvm/lib/IR/DebugLoc.cpp b/llvm/lib/IR/DebugLoc.cpp
index 88f2dbc..075f295 100644
--- a/llvm/lib/IR/DebugLoc.cpp
+++ b/llvm/lib/IR/DebugLoc.cpp
@@ -58,12 +58,8 @@
   if (Col > 255) Col = 0;
   if (Line >= (1 << 24)) Line = 0;
 
-  LLVMContext &Context = Scope->getContext();
-  Type *Int32 = Type::getInt32Ty(Context);
-  Metadata *Elts[] = {ConstantAsMetadata::get(ConstantInt::get(Int32, Line)),
-                      ConstantAsMetadata::get(ConstantInt::get(Int32, Col)),
-                      Scope, InlinedAt};
-  return getFromDILocation(MDNode::get(Context, Elts));
+  return getFromDILocation(
+      MDLocation::get(Scope->getContext(), Line, Col, Scope, InlinedAt));
 }
 
 /// getAsMDNode - This method converts the compressed DebugLoc node into a