[plsql] segment_attributes_clause contains table_compression but it shouldn't.

[kaby76]

segment_attributes_clause contains table_compression but it shouldn't. It was introduced because someone couldn't figure out how to avoid the issues of taking Kleene closures of nullable symbols, which are in the PLSQL spec. This is probably because the railroad diagrams were derived by reverse-engineering code for a parser, or because the railroad diagrams are based on an LR grammar.

For an analysis, see #4366 (comment).