PR07: Test the parsing of == and += in macro definitions.

Trip the parser so we don't get any further.
@>

1. Test with no equals.
@$@<Sloth@>@{No equals in this macro definition.@}

2. Test with ==.
@$@<Sloth with equals@>==@{No equals in this macro definition.@}

3. Test with +=.
@$@<Sloth with plus@>+=@{No equals in this macro definition.@}

4. Test with syntax errors.

@$@<Error1@>++@{No equals in this macro definition.@}
@A@<Error recovery point@>

@$@<Error2@>@+=@{No equals in this macro definition.@}
@A@<Error recovery point@>

@$@<Error3@>+==+@{No equals in this macro definition.@}
@A@<Error recovery point@>

@$@<Error4@>=+@{No equals in this macro definition.@}
@A@<Error recovery point@>

@$@<Error4@>@=@=@{No equals in this macro definition.@}
@A@<Error recovery point@>

@$@<Error4@>@+@=@{No equals in this macro definition.@}
@A@<Error recovery point@>