Merge branch 'jk/compat-timegm' into pu

* branch jk/compat-timegm:
  compat/timegm: new compat function for systems lacking timegm()
  Makefile: re-include cgit.conf in cgit.mk

Submitted to cgit@hjemli.net but not applied.

Need to see if there is an alternative to introducing a compat function.
Doing the back and forth in the local timezone is mostly good enough,
but doesn't handle DST correctly.
Merge branch 'log-follow-files' into pu

* branch log-follow-files:
  log: allow users to follow a file
  shared: make cgit_diff_tree_cb public

Submitted to cgit@hjemli.net.