Bugs fixed

PDB with a box of size 1 Angstrom are interpreted as having no PBC

PDB files with structures not determined from X-ray should have a unit-cell with P=1 and dimensions of 1 Angstrom to indicate no periodic boundary conditions. GROMACS now interprets such structures as not having PBC.

Issue 4645, Issue 5679

PDB trajectory output now writes correct per-frame PBC type

When writing PDB trajectories, the PBC type of the system was ignored and instead guessed from the box. As a result, the CRYST1 record was written incorrectly for screw PBC (wrong space group and cell length).

Analysis tools now always process time values in double precision

This avoids picking incorrect frames when times values are large.