Update almost all tests (except co19) to use the new try-catch syntax.

tests/language/prefix16_test.dart

Index: tests/language/prefix16_test.dart
diff --git a/tests/language/prefix16_test.dart b/tests/language/prefix16_test.dart
index ff248b02e90c1ca04ec7e3358749030973f2e777..15cea9723b36fbde179a8d04d5f5660f42169619 100644
--- a/tests/language/prefix16_test.dart
+++ b/tests/language/prefix16_test.dart
@@ -18,7 +18,7 @@ isCheckedMode() {
     var i = 1;
     String s = i;
     return false;
-  } catch(var e) {
+  } catch (e) {
     return true;
   }
 }
@@ -28,7 +28,7 @@ main() {
     bool got_type_error = false;
     try {
       myFunc i = 0;
-    } catch (TypeError error) {
+    } on TypeError catch (error) {
       got_type_error = true;
     }
     // Type error in checked mode only.
@@ -39,7 +39,7 @@ main() {
     try {
       // In production mode, malformed myFunc is mapped to (Dynamic) => Dynamic.
       Expect.isTrue(((int x) => x) is myFunc);
-    } catch (TypeError error) {
+    } on TypeError catch (error) {
       got_type_error = true;
     }
     // Type error in checked mode only.