Rename Handler as DiagCtxt.

Author: nnethercote

src/concurrency_limiter.rs

@@ -46,7 +46,7 @@ impl ConcurrencyLimiter {
  }
  }
 
- pub(super) fn acquire(&mut self, handler: &rustc_errors::Handler) -> ConcurrencyLimiterToken {
+ pub(super) fn acquire(&mut self, handler: &rustc_errors::DiagCtxt) -> ConcurrencyLimiterToken {
  let mut state = self.state.lock().unwrap();
  loop {
  state.assert_invariants();