Delete the redundant future wait_and_get APIs

[agrippa]

Title pretty much says it. The future wait_and_get() is now redundant with wait() as wait() also returns the datum placed in the associated promise. Rather than have two APIs, this change simply deletes the wait_and_get API in the C and C++ APIs.

[srirajpaul]

Changes look good.

Few additions There are few tests which include wait_and_get 1) modules/cuda/test/async_simd.cu: int dArr = (int )allocation->wait_and_get(); 2) modules/cuda/test/async_simd.cu: int hArr = (int )allocation->wait_and_get(); 3) test/cpp/promise/async_future_await_at.cpp: int result = fut->wait_and_get();

The wait_and_get in test/cpp/promise/async_future_await_at.cpp is causing travis to fail.

[agrippa]

@srirajpaul fixes are ready, looks good?

[srirajpaul]

Looks good.