kasan: show gcc version requirements in Kconfig and Documentation

The documentation shows a need for gcc > 4.9.2, but it's really >=.  The
Kconfig entries don't show require versions so add them.  Correct a
latter/later typo too.  Also mention that gcc 5 required to catch out of
bounds accesses to global and stack variables.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 01e76903f655a4d88c2e09d3182436c65f6e1213
Git-repo: https://github.com/torvalds/linux.git


Change-Id: I88e1c907294327972176448e0b3335fe65e82c4d
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>