hello-wuffs-c: update endwhile syntax

Also fix lang/check
diff --git a/hello-wuffs-c/parse.wuffs b/hello-wuffs-c/parse.wuffs
index 2e6ba6f..1184de5 100644
--- a/hello-wuffs-c/parse.wuffs
+++ b/hello-wuffs-c/parse.wuffs
@@ -37,7 +37,7 @@
         // Uncomment this assertion to see what facts are known here.
         // assert false
         this.val = (10 * this.val) + (c as base.u32)
-    } endwhile
+    }
 }
 
 pub func parser.value() base.u32 {
diff --git a/lang/check/check_test.go b/lang/check/check_test.go
index c47aca7..f1115da 100644
--- a/lang/check/check_test.go
+++ b/lang/check/check_test.go
@@ -86,7 +86,7 @@
 			{
 				// Redundant, but shows the labeled jump syntax.
 				continue.label
-			} endwhile.label
+			}.label
 		}
 	`) + "\n"