Checkpoint file for mplrs/mplrs1

The checkpoint file has the following format in v 6.2.

First is a line giving the checkpoint format version -- currently "mplrs3".
Next is a line with five unsigned longs giving the counting stats on number of rays, number of vertices, number of bases, number of facets, number of integer vertices seen so far.
Next is a line giving the volume computed so far, as a string. 
Then the list of cobases in L is given, one per line.

For example, 

mplrs3
0 29 7387 0 16
0
7 0 179 0   15 22 24 26 28 30 31 32 34 35
7 0 178 0   13 22 24 26 28 30 31 32 34 36
7 0 176 0   13 15 20 22 24 26 28 30 32 34
...

is the start of a checkpoint file produced on mp5.ine with -id 1.

The number of cobasis lines in a checkpoint file is not specified, so a prefix of a checkpoint file is a valid checkpoint file as long as it contains a complete header. 
The checkpoint can be manually split as desired, by splitting the list of cobases into two files.  The three-line header can be left unmodified in one file, and the counting stats and volume all zeroed in the other.

Notes:
1. mplrs/mplrs1 can restart from checkpoint files produced by previous versions,but previous versions cannot restart from checkpoint files produced by later versions.  

2.The volume was not recorded prior to v 6.2, and so restarting from an earlier checkpoint file may produce incorrect volume output (a warning is printed in such cases).  

3. The checkpoint file format is likely to change in future versions.

4. "mplrs2" format is the same but omits volume.  

5."mplrs1" format is the same as mplrs2 but used signed 32-bit integers for counting stats