DI: Remove DW_TAG_arg_variable and DW_TAG_auto_variable

Remove the fake `DW_TAG_auto_variable` and `DW_TAG_arg_variable` tags,
using `DW_TAG_variable` in their place Stop exposing the `tag:` field at
all in the assembly format for `DILocalVariable`.

Most of the testcase updates were generated by the following sed script:

    find test/ -name "*.ll" -o -name "*.mir" |
    xargs grep -l 'DILocalVariable' |
    xargs sed -i '' \
      -e 's/tag: DW_TAG_arg_variable, //' \
      -e 's/tag: DW_TAG_auto_variable, //'

There were only a handful of tests in `test/Assembly` that I needed to
update by hand.

(Note: a follow-up could change `DILocalVariable::DILocalVariable()` to
set the tag to `DW_TAG_formal_parameter` instead of `DW_TAG_variable`
(as appropriate), instead of having that logic magically in the backend
in `DbgVariable`.  I've added a FIXME to that effect.)

llvm-svn: 243774
diff --git a/llvm/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll b/llvm/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
index 86a1647..958f121 100644
--- a/llvm/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
+++ b/llvm/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
@@ -93,11 +93,11 @@
 !11 = !{!13}
 !13 = !DISubprogram(name: "fn", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 1, file: !24, scope: !14, type: !7, function: i32 (i32)* @fn, variables: !1)
 !14 = !DIFile(filename: "simple2.c", directory: "/private/tmp")
-!15 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "a", line: 2, arg: 1, scope: !5, file: !6, type: !9)
+!15 = !DILocalVariable(name: "a", line: 2, arg: 1, scope: !5, file: !6, type: !9)
 !16 = !DILocation(line: 2, scope: !5)
 !17 = !DILocation(line: 4, scope: !18)
 !18 = distinct !DILexicalBlock(line: 3, column: 0, file: !23, scope: !5)
-!19 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "a", line: 1, arg: 1, scope: !13, file: !14, type: !9)
+!19 = !DILocalVariable(name: "a", line: 1, arg: 1, scope: !13, file: !14, type: !9)
 !20 = !DILocation(line: 1, scope: !13)
 !21 = !DILocation(line: 2, scope: !22)
 !22 = distinct !DILexicalBlock(line: 1, column: 0, file: !24, scope: !13)