Some PNaCL compatibility fixes.

* Removed a few useless and non-standard #includes.
* Made OS::GetCurrentProcessId compile without syscall.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/508933002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23459 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Disable some changes tests on ARM64. Also, fix the changes lowering to not use the more expensive TruncateFloat64ToInt32, but to use ChangeFloat64ToInt32/ChangeFloat64ToUint32, as it was before.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/512753002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23460 ce2b1a6d-e550-0410-aec6-3dcde31c8c00