dpdkstrip: add a preprocessor tool for stripping dpdk blocks

dpdkstrip: add a preprocessor tool for stripping dpdk blocks

Normally, in C code, pre-processing macros can be used to enable/disable
specific functionality based on switches passed to configure.  This works
for DPDK using the --with-dpdk flag, which sets the DPDK_NETDEV define to
the appropriate value.

However, not all files are processed with the C pre-processor.  For those
files which are not, this commit adds a new pre-processor tool for .in
files to either include or exclude those stanzas as appropriate.

Signed-off-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Russell Bryant <russell@ovn.org>