PR10: Test syntactic error recovery. 1. Test recovery at top parsing level. @< @A@ 2. Test recovery inside macro definition. @$@@>==@{ Walrus@} @$@==@{ @ 3. Test recovery inside actual parameter list in macro definition. @$@==@{ @@(@"aardvark@> @} @A@ 4. Test EOF in the middle of a complicated construct. The following makes the end of the file looked chopped off, but it is actually intentional. @$@==@{ @@(@"aardva