jasper: bump version to 1.900.31 (security)

Fixed CVEs:
 - CVE-2016-9387
 - CVE-2016-9388
 - CVE-2016-9389
 - CVE-2016-9390
 - CVE-2016-9391
 - CVE-2016-9392
 - CVE-2016-9393
 - CVE-2016-9394
 - CVE-2016-9395
 - CVE-2016-9396
 - CVE-2016-9397
 - CVE-2016-9398
 - CVE-2016-9399
 - CVE-2016-9557
 - CVE-2016-9560

Changes to jasper.mk:
 - Switched site method to GitHub. 1.900.31 is not released as a tarball
   in the official website.
 - Autoreconf necessary since there isn't any configure script. We need
   to generate it.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>