Patch 0/6 virtual address space randomisation

[Arjan van de Ven <arjan@infradead.org>]

The randomisation patch series introduces infrastructure and functionality
that causes certain parts of a process' virtual address space to be
different for each invocation of the process. The purpose of this is to
raise the bar on buffer overflow exploits; full randomisation makes it not
possible to use absolute addresses in the exploit.

This first series only does a partial randomisation, future series will
randomize other parts of the virtual address space as well.

01-sysctl-A0			- introduce a sysctl to enable/disable
02-randomize-infrastructure	- infrastructure helpers
03-PF_RANDOMIZE			- per process flag to enable/disable
04-stack			- start randomizing the stack pointer
05-mmap				- start randomizing mmap addresses
06-default-enable		- enable randomisation by default (for -mm testing only) 

This series does NOT randomize the brk() area and does not yet add support
for PIE binaries. This I will leave to a next series; this one should first
settle down.

Signed-off-by: Arjan van de Ven <arjan@infradead.org>