[Utils] Add highlighting definition for byref IR attribute

This patch assumes `byref` can be handled identically to `byval`.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D85768

utils/kate/llvm.xml

@@ -68,6 +68,7 @@
       <item> zeroext </item>
       <item> signext </item>
       <item> inreg </item>
+      <item> byref </item>
       <item> byval </item>
       <item> sret </item>
       <item> noalias </item>

utils/vim/syntax/llvm.vim

@@ -55,6 +55,7 @@ syn keyword llvmKeyword
       \ available_externally
       \ blockaddress
       \ builtin
+      \ byref
       \ byval
       \ c
       \ catch

utils/vscode/llvm/syntaxes/ll.tmLanguage.yaml

@@ -152,6 +152,7 @@ patterns:
             \\bavailable_externally\\b|\
             \\bblockaddress\\b|\
             \\bbuiltin\\b|\
+            \\bbyref\\b|\
             \\bbyval\\b|\
             \\bc\\b|\
             \\bcatch\\b|\