UPDATE 1-Feted in Gaza, Hamas leader to attend "victory rally"

* Meshaal ends decades of exile, makes first trip to Gaza * Hamas leader likely to push for Palestinian unity * Huge crowds expected at mass rally in Gaza City (Adds quotes, colour) GAZA, Dec 8 (Reuters) - After receiving a hero's welcome onhis return from decades in exile, Hamas leader Khaled Meshaalwill attend a rally in Gaza on Saturday to mark the founding ofhis Islamist group and celebrate ...