Bug 1102209 - Remove use of CodeGen::JoinInstructions in the Linux sandboxing code. r=kang

This reorganizes SandboxAssembler to stack up the policy rules and
traverse them in reverse order to build the filter DAG from tail to head
(i.e., starting with "deny all" and prepending allow and return-errno
rules).  Thus, this code will continue to work (perhaps with minor
changes, such as to the NodePtr typedef) with future versions of the
Chromium sandbox code that don't allow mutating the filter program with
the JoinInstructions method.
Bug 1093334 - Import more headers from Chromium rev 9522fad406dd161400daa518075828e47bd47f60. r=kang
Bug 1093334 - Adjust includes of Linux sandboxing headers from Chromium. r=kang

Also re-sorts some of the includes into something closer to the style guide.
Bug 1093334 - Delete unnecessary copies of Chromium headers in security/sandbox/linux. r=kang