Change the hex literal processing so that only the SQL parser understands
hex literals.  Casting and coercing string literals into numeric values does
not understand hexadecimal integers.  This preserves backwards compatibility.
Also:  Throw an error on any hex literal that is too big to fit into 64 bits.
Remove a surplus function prototype.  #ifdef code that is not used when
hex integers are omitted at compile time.
Enhancements to the hex literal tests.