Fix divide-by-zero bug in statistics.c

GET_LOCAL_SAC did not check if the two entries had different time stamps
and could therefore cause a divide-by-zero. x86 doesn't fault on that -
it's still wrong. This now calls a function that does proper checking of
all the values involved in the calculation.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
A bit of tweaking on Releasenotes.txt

I like to mention the most important features first (thus the profile is
added to the introductory chapter).

Moving word 'also' to different place on the GPS paragraph to indicate
that map is not the only way of inserting GPS coordinates.

JDivelog import was in 2.1 release so removed from here (it is actually
written JDiveLog - with capital L - should probably be fixed in user
manual).

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>