Clarify that new lints are are T-lang changes

They therefore require an RFC.

compiler_changes.md

@@ -21,6 +21,7 @@ submitted later if there is scope for large changes to the language RFC.
 
 ## Changes which need an RFC
 
+* New lints (these fall under the lang team)
 * Large refactorings or redesigns of the compiler
 * Changing the API presented to syntax extensions or other compiler plugins in
   non-trivial ways

lang_changes.md

@@ -1,6 +1,8 @@
 # RFC policy - language design
 
-Pretty much every change to the language needs an RFC.
+Pretty much every change to the language needs an RFC. Note that new
+lints (or major changes to an existing lint) are considered changes to
+the language.
 
 Language RFCs are managed by the language sub-team, and tagged `T-lang`. The
 language sub-team will do an initial triage of new PRs within a week of