AArch64-port: Initial porting effort for AArch64

This still needs more testing; adding this as a baseline.

Refer to https://github.com/dmtcp/dmtcp/pull/4 for review
comments.

Testing:
 - build DMTCP for x86-64
   + make check
 - build DMTCP for AArch64 on Foundation model v2
   (running Ubuntu 14.04)
   + Basic tests



git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2862 ba6dc0ae-232f-0410-883f-9ebac64fc565