eal: introduce memory management wrappers

eal: introduce memory management wrappers

Introduce OS-independent wrappers for memory management operations used
across DPDK and specifically in common code of EAL:

* rte_mem_map()
* rte_mem_unmap()
* rte_mem_page_size()
* rte_mem_lock()

Windows uses different APIs for memory mapping and reservation, while
Unices reserve memory by mapping it. Introduce EAL private functions to
support memory reservation in common code:

* eal_mem_reserve()
* eal_mem_free()
* eal_mem_set_dump()

Wrappers follow POSIX semantics limited to DPDK tasks, but their
signatures deliberately differ from POSIX ones to be more safe and
expressive. New symbols are internal. Being thin wrappers, they require
no special maintenance.

Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>