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/objc-property-void.ll b/llvm/test/DebugInfo/X86/objc-property-void.ll
index 0737fe2..45d3512 100644
--- a/llvm/test/DebugInfo/X86/objc-property-void.ll
+++ b/llvm/test/DebugInfo/X86/objc-property-void.ll
@@ -96,9 +96,9 @@
 !21 = !{i32 2, !"Dwarf Version", i32 2}
 !22 = !{i32 1, !"Debug Info Version", i32 3}
 !23 = !{!""}
-!24 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "self", arg: 1, flags: DIFlagArtificial | DIFlagObjectPointer, scope: !10, type: !25)
+!24 = !DILocalVariable(name: "self", arg: 1, flags: DIFlagArtificial | DIFlagObjectPointer, scope: !10, type: !25)
 !25 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, baseType: !4)
 !26 = !DILocation(line: 0, scope: !10)
-!27 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "_cmd", arg: 2, flags: DIFlagArtificial, scope: !10, type: !28)
+!27 = !DILocalVariable(name: "_cmd", arg: 2, flags: DIFlagArtificial, scope: !10, type: !28)
 !28 = !DIDerivedType(tag: DW_TAG_typedef, name: "SEL", line: 5, file: !5, baseType: !15)
 !29 = !DILocation(line: 5, scope: !10)