[PATCH] SubmittingPatches: add a note about "format=flowed" when sending patches

Add a note about "format=flowed" when sending patches and explain how to
fix mozilla.  Thunderbird has the similar options.

Signed-off-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>