some errors (?) in the JPQL grammar

[gavinking]

While working on the Query spec, I ran into the following things:

state_valued_path_expression ::=
    state_field_path_expression | *general_identification_variable*

How can an identification variable can't represent a basic value?

type_discriminator ::=
    TYPE(general_identification_variable |
        single_valued_object_path_expression |
        *input_parameter*)

What was input_parameter doing there?

single_valued_path_expression ::=
    qualified_identification_variable |
    **TREAT(qualified_identification_variable AS subtype)** |
    state_field_path_expression |
    single_valued_object_path_expression

What could possibly have been the intention of allowing TREAT(ENTRY(...)), TREAT(KEY(...)), TREAT(VALUE(...)) there, in a location where TREAT() is not even allowed for a regular identification_variable.

I think these things are so clearly wrong that we might as well fix them here too.