Uses class in inyerface and implementation

[Mahendran]

Wats the need for two uses class in unit file both in interface and implementation file....

[Loïs Bégué]

At least 2 reasons:
- "uses" in implementation won't be exposed outside the unit (similar to local vs. global variables...)
- different levels of "uses" clauses allow (under certain circumstances) a kind of cross-dependency between 2 units.