Prohibit multiple load() statements from appearing on the same line

This is an incompatible change, but it's an obvious bug.

RELNOTES[INC]: Fixed a bug whereby multiple load() statements could appear on the same line

PiperOrigin-RevId: 161070399
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Parser.java b/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
index 06f0ac9..7bc94c1 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
@@ -1116,6 +1116,7 @@
 
     LoadStatement stmt = new LoadStatement(importString, symbols);
     list.add(setLocation(stmt, start, token.left));
+    expectAndRecover(TokenKind.NEWLINE);
   }
 
   /**