enable C++ target for OptiQL
fix C++ bug: declare runtime _cond variable only once for each target
enable Arguments op for C++ only when needed
FIX: For scala target _cond variable should be generated for all possible schedules
C++ fix: load/store JNI objects to share across C++ threads.
Use case: when a C++ thread tries to update to JVM for a data structure created from another C++ thread.
(test case: Delite OptiML VectorSuite VectorUpdatesRunner)
C++ fix: Initialize sync object of type string to string() instead of NULL.
C++ fix: off-by-one error for parallel IO (bug was skipping the first line assigned to each thread)
C++ fix: missing notify/await nodes
C++ fix: structural equality for DeliteStructs
C++ fix: reference sync objects only when actually generated (locations passed to writeJNIInitializer)