git: Tell git send-email where to send patches.

git: Tell git send-email where to send patches.

I've been using

  git send-email --annotate --suppress-from --to=gcc-patches@gcc.gnu.org \
  ${@:-HEAD^} ':!*/ChangeLog' ':!*configure'

for sending most patches, but it occurs to me that it would be useful to put
the To: address in the configury.

If someone were feeling ambitious, they could write a script to analyze a
patch and add the relevant maintainers to To: or CC:.

contrib/ChangeLog:

	* gcc-git-customization.sh: Configure sendemail.to.