Fixes:
- CVE-2016-1248: vim before patch 8.0.0056 does not properly validate values
for the 'filetype', 'syntax' and 'keymap' options, which may result in the
execution of arbitrary code if a file with a specially crafted modeline is
opened.
- CVE-2017-5953: vim before patch 8.0.0322 does not properly validate values
for tree length when handling a spell file, which may result in an integer
overflow at a memory allocation site and a resultant buffer overflow.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>