[s390] The s390 port.

This change contains the cpu/s390 and os_cpu/linux_s390 files of the linuxs390 port.

The port supports:
  - the template interpreter
  - the C1 compiler
  - the C2 compiler
  - a large number of instrinsics
  - all GCs
  - many optimization options as, e.g., BiasedLocking.
It does not support or we never tested:
  - the servicability agent
  - class data sharing
  - NMT

It supports all IBM z/Architecture processors newer and including z10.
It will not start up on older processors. It supports RHEL 6
and SLES 11 and newer.

It needs to be built with at least gcc 4.8.

It is based on SAP's internal, productive Java 8 Jvm. It passes
the same set of jtreg tests as linuxx86_64 does. Further we tested
it with SPEC benchmarks, SAP applications and most jck tests.