Update to build against the latest revision of linux_syscall_support.h

The prctl() calls must be updated following this LSS change:
https://code.google.com/p/linux-syscall-support/source/detail?r=24

BUG=none
TEST=build

Review URL: https://breakpad.appspot.com/627002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1210 4c0a9323-5329-0410-9bdc-e9ce6186880e