Inclusive Exclusive Collective Summation Operation

[markbrown314]

Add an inclusive (shmem_sum_inscan) and exclusive (shmem_sum_exscan) collective summation operation.

See OpenSHMEM specification section 9.10.10

[markbrown314]

@avincigu please close is this task if it is resolved with issue #1154 or link additional related PRs to this task ticket.

[avincigu]

Closing as it has been implemented in #1154