Merge branch 'android-3.18' into android-goldfish-3.18-dev

191df757 UPSTREAM: ARM: 8494/1: mm: Enable PXN when running non-LPAE kernel on LPAE processor
7877b968 BACKPORT: ARM: 8235/1: Support for the PXN CPU feature on ARMv7
cbad12fb ANDROID: dm: android-verity: Allow android-verity to be compiled as an independent module
...
012b0adc FROMLIST: security,perf: Allow further restriction of perf_event_open
925d82a4 BACKPORT: perf tools: Document the perf sysctls
c5c74d03 ANDROID: dm: use default verity public key

Change-Id: I797f122ee496c70ee0e88105eda3cfbdc166652a