In general, merging process should not be very difficult, but we need to
track GCC-specific patches carefully.  Here is a general list of actions
required to perform the merge:

* Checkout recent GCC tree.
* Run merge.sh script from the libffi directory.
* Add new files and remove old files if needed.
* Apply all needed GCC-specific patches to libffi (note that some of
  them might be already included to upstream).  The list of these patches
  is stored into LOCAL_PATCHES file.  May need to re-run autogen.sh to
  regenerate configure and Makefile.in files.
* Send your patches for review to GCC Patches Mailing List (gcc-patches@gcc.gnu.org).
* Update LOCAL_PATCHES file when you've committed the whole patch set with new revisions numbers.