Added missing include required by recent versions of asm/uaccess.h

[neilwhelchel]

This fixes a compile error with recent versions of the linux kernel, in my case 4.14.134:
./arch/x86/include/asm/uaccess.h:33:9: error: dereferencing pointer to incomplete type current->thread.addr_limit = fs;
I have not tested this against older versions of the kernel, but it seems safe to include traps.h as it has an include guard.

[andypugh]

I did an experiment to see if another possible fix worked last night.
(I should have done it in an experimental branch, and really I think that a fix belongs in 2.8 or maybe even 2.7)
Based on https://lkml.org/lkml/2017/9/30/189 I put in 0dbbfb3

But I think I will roll that back and use kernel version macros. so that the change only happens post 2.14. Thoughts.

[andypugh]

Thanks for bringing this to to our attention.
In the end I have decided to use the fix recommended here:
https://lkml.org/lkml/2017/9/30/189
via 5ffa41e
But please don't let this dissuade you from further pull requests.

[neilwhelchel]

Hello Andy, good catch! Strangely enough I knew about how the headers are being changed around in the kernel, but I totally missed that when made this fix. I guess I had a bad case of tunnel vision.