ivshmem: library changes for mmaping using ivshmem

ivshmem: library changes for mmaping using ivshmem

These library changes provide a new Intel DPDK feature for communicating
with virtual machines using QEMU's IVSHMEM mechanism.

The feature works by providing a command line for QEMU to map several hugepages
into a single IVSHMEM device. For the guest to know what is inside any given IVSHMEM
device (and to distinguish between Intel(R) DPDK and non-Intel(R) DPDK IVSHMEM
devices), a metadata file is also mapped into the IVSHMEM segment. No work needs to
be done by the guest application to map IVSHMEM devices into memory; they are
automatically recognized by the Intel(R) DPDK Environment Abstraction Layer (EAL).

Changes in this patch:
* Changes to EAL to allow mapping of all hugepages in a memseg into a single file
* Changes to EAL to allow ivshmem devices to be transparently mapped in
  the process running on the guest.
* New ivshmem library to create and manage metadata exported to guest VM's
* New ivshmem compilation targets
* Mempool and ring changes to allow export of structures to a VM and allow
  a VM to attach to those structures.
* New autotests to unit tests this functionality.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>