Fixed GMX_DD_DUMP_GRID

The pdb format string no longer matched the parameters it was given

Change-Id: I682154a0986fdbd73ae414264982a68fed164c87
Fix minor wallcycle output issues

Document 19-character wcn name restriction better.

Enforce 19-character wcn name restriction better. The new behaviour
correctly truncates a wcn[] that is too long for the 19-printing
character field width of the wallcycle table.

Compress two names into one field for GMX_CYCLE_ALL correctly. The
previous version was buggy because the first call to snprintf()
resulted in 0 == buf[8], which suppressed output of the second name
completely. The previous version's second call to snprintf() was
probably wrong similarly.

Change-Id: I430ca6eb2bccfe3775e58bae4b6fc3326bcde706