[subset] --recalc-timestamp does not work in OTF

In pyftsubset --help, timestamp options are described as follows:

  --recalc-timestamp
      Set font 'modified' timestamp to current time.
  --no-recalc-timestamp
      Do not modify font 'modified' timestamp. [default]

But actually pyftsubset seems to never recalc timestamp, even if --recalc-timestamp is set.

[justvanrossum]

Or it could be done by TTFont().save(), TTFont has the same problem of not recalculating the time stamp when head was not loaded.

[anthrotype]

maybe the subsetter should decompile head whenever --recalc-timestamp option is passed, so it will get recompiled with the updated timestamp.