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/generate-odr-hash.ll b/llvm/test/DebugInfo/X86/generate-odr-hash.ll
index 7ac9a69..293c92a 100644
--- a/llvm/test/DebugInfo/X86/generate-odr-hash.ll
+++ b/llvm/test/DebugInfo/X86/generate-odr-hash.ll
@@ -264,12 +264,12 @@
 !43 = !{i32 2, !"Dwarf Version", i32 4}
 !44 = !{i32 1, !"Debug Info Version", i32 3}
 !45 = !{!"clang version 3.5 "}
-!46 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "b", line: 7, scope: !22, file: !23, type: !47)
+!46 = !DILocalVariable(name: "b", line: 7, scope: !22, file: !23, type: !47)
 !47 = !DICompositeType(tag: DW_TAG_structure_type, name: "baz", line: 6, size: 8, align: 8, file: !1, scope: !22, elements: !2)
 !48 = !DILocation(line: 7, scope: !22)
 !49 = !DILocation(line: 8, scope: !22)
 !50 = !DILocation(line: 29, scope: !26)
-!51 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1, flags: DIFlagArtificial | DIFlagObjectPointer, scope: !27, type: !52)
+!51 = !DILocalVariable(name: "this", arg: 1, flags: DIFlagArtificial | DIFlagObjectPointer, scope: !27, type: !52)
 !52 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, baseType: !28)
 !53 = !DILocation(line: 0, scope: !27)
 !54 = !DILocation(line: 25, scope: !27)