Non-decimal integer literals 
 
Add support for hexadecimal, octal, and binary integer literals:
 
    0x42F
    0o273
    0b100101
 
per SQL:202x draft.
 
This adds support in the lexer as well as in the integer type input
functions.
 
Reviewed-by: John Naylor <john.naylor@enterprisedb.com>
Reviewed-by: Zhihong Yu <zyu@yugabyte.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/b239564c-cad0-b23e-c57e-166d883cb97d@enterprisedb.com