Copy full headers directory into SDK

The dpdk-dev SDK package is arch-dependent, as it ships a number of
binary executables.
Also using RTE_SDK does not support the multiple level of headers, so
instead of symlinking into /usr/include/dpdk copy the full set of
headers into /usr/share/dpdk/TARGET/include
Given dpkg cannot replace a symlink with a directory automatically
also generate a preinst file to handle it manually on upgrade.

Change-Id: I1fb8fbe424b8ef015c04062f2cffe9f2b9ffe02f
Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>