executor.add_function needs to add multiple functions simultaneously

[Matt Giuca]

In the LLVM backend, we actually compile functions when they are added to the environment. If multiple functions are added together, they may depend on one another. The current interactive code folds over all of the functions and inserts them one by one -- this means dependencies may not yet be satisfied.

Change the executor interface so that add_function becomes add_functions. The individual backend can then decide how to deal with accepting a set of functions at a time. Interactive would no longer fold over them, just pass all of them to executor.add_functions.

[Matt Giuca (mgiuca)]

Fixed in trunk r1261.