InSituMPI AsyncSendVariable element type

Created by: bradking

The code in InSituMPIWriter::AsyncSendVariable here is:

const size_t blockStart = seek.first;
const size_t blockSize = seek.second - seek.first;

MPI_Isend(blockInfo.Data + blockStart, blockSize, MPI_CHAR,

The type of blockInfo.Data is T so blockInfo.Data + blockStart computes a buffer offset in multiples of sizeof(T), but the size and element type use units of sizeof(char). This inconsistency is likely a bug.