The header was missing the extern "C" directive which causes name
mangling of functions by C++ compilers, leading to linker errors
complaining of undefined references to these functions.
Fixes: 4958ca3a443a ("mbuf: support dynamic fields and flags")
Cc: stable@dpdk.org
Signed-off-by: Ashish Sadanandan <ashish.sadanandan@gmail.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>