Add test case for trailing junk after numeric literals

Add test case for trailing junk after numeric literals

PostgreSQL currently accepts numeric literals with trailing
non-digits, such as 123abc where the abc is treated as the next token.
This may be a bit surprising.  This commit adds test cases for this;
subsequent commits intend to change this behavior.

Reviewed-by: John Naylor <john.naylor@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/b239564c-cad0-b23e-c57e-166d883cb97d@enterprisedb.com