Added missing SQL operators for each grammar.

Added bitwise operators using the following grid:

        MySQL  PgSQL  SQLite  MSSQL
AND     &      &      &       &
AND-E                         &=
OR      |      |      |       |
OR-E                          |=
XOR     ^      #              ^
XOR-E                         ^=
L-SHFT  <<     <<     <<
R-SHFT  >>     >>     >>

Additionally added:

- SQLite's == operator,
- MSSQL's not-greater-than (!>), not-less-than (!<) operators.

I have not added NOT (universally '~') as I'm not sure how this would be used
with where($col, $op, $val).