buildroot

linux: add conditional patch for timeconst.pl

Kernels older than 3.9 (not counting stable releases) used the
timeconst.pl perl script for their build process.
The problem with this script is that it used deprecated perl features,
namely defined(@array) which was removed for the perl 5.22 release,
causing build failure of older kernels on newer distributions.

To fix this instead of going the hard way (moving to the new
timeconst.bc script) use the easy way by patching timeconst.pl with an
upstream patch used for stable releases.

First try a dry-run on the patch to see if it applies, if it does then
call a proper APPLY_PATCHES to it.

Tested against an arbitrary 2.6.30 kernel (applies and builds), against
4.4.1 for a missing timeconst.pl (does not apply since it's missing) and
3.8.13 (does not apply since it's fixed already).

Known broken distributions: fedora 23, debian testing (stretch) and unstable
(sid).

Signed-off-by: Gustavo Zacarias <gustavo.zacarias@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>