Makefile always checks the existence of host's NAT-PMP header,
which results in internal NAT-PMP code being used if it's missing.

Add a patch to make it check targets' header instead.

Use aligned_alloc() instead of valloc() in case of uclibc.

Signed-off-by: DENG Qingfang <dengqf6@mail2.sysu.edu.cn>