Revision 172

Just indented correctbid and nat2gcm.

The procedure read_reanalyse just reads the next time slab every time
it is called. No use keeping track of the time index in the calling
procedure, guide. It is simpler to do it in read_reanalyse. Also
simpler to read the number of vertical levels in read_reanalyse than
in guide, since we have already in read_reanalyse the input of
pressure levels. We then have to make the arrays containing reanalyses
static allocatable instead of automatic. Also only read pressure
levels at the first call of read_reanalyse instead of at every call.

masserea2 not used in guide. Remove it down the chain in
read_reanalyse and reanalyse2nat.