[clang] [Clang] raise extension warning for unknown namespaced attributes (PR #120925)

[Aaron Ballman via cfe-commits]

================
@@ -606,6 +606,8 @@ Attribute Changes in Clang
 
 - Clang now disallows the use of attributes after the namespace name. (#GH121407)
 
+- Clang now raises warnings for unknown namespaced attributes only in pedantic mode (#GH120875).
----------------
AaronBallman wrote:

This is incorrect; it adds a new diagnostic group rather than a pedantic warning.

https://github.com/llvm/llvm-project/pull/120925