Fixes FTBFS on recent gcc:
logrotate.c: In function 'prerotateSingleLog':
logrotate.c:1328:6: error: 'strncat' specified bound depends on the length of the source argument [-Werror=stringop-overflow=]
      strncat(tempstr, rotNames->baseName, baseLen - extLen);
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
logrotate.c:1320:19: note: length computed here
  size_t baseLen = strlen(rotNames->baseName);
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~
logrotate.c:1347:2: error: 'strncat' specified bound depends on the length of the source argument [-Werror=stringop-overflow=]
  strncat(tempstr, rotNames->baseName,
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   strlen(rotNames->baseName) - strlen(log->extension));
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
logrotate.c:1348:3: note: length computed here
   strlen(rotNames->baseName) - strlen(log->extension));
   ^~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors