Non-buffered gmx_tx_rx_real in partdec

Non-buffered gmx_tx_real implementation added for the particle decomposition part
of the code.
Memory allocation of buffers involved have been replaced by symmetric allocations.
A word of cation with state_global: Since it is used in the write_traj functions,
which contains calls to gmx_tx_rx_real , it has to be allocated in symmetric memory.
However, state global is different in each node (as the master loads its values from a file
whereas others are initialisez somewhere else).
State-global relevant pointers (i.e x, sd_X, ...) are replaced by symm after the creation
of the state_local , thus preserving the data.
Since state-global is apparently not freed anywhere, we do not get further errors.