[MOD] Package-protected StaticContext#xquery3 flag.
[MOD] Updating the stack-frames code.
[MOD] GFLWOR optimizations.
[ADD] General inlining.
[ADD] Expr#copy() for copying expressions and some static typing.
[MOD] Generalized and simplified the Expr visitor.
[ADD] Function inlining implemented.
[DEL] Expr#remove(Var) not needed any longer.
[MOD] cleanup of static variables code.
[MOD] Better strategy for compiling functions and static variables.
[MOD] The stack is now a single array, also some inlining fixes.