strdup() prototype doesn't live in stdlib.h .

Add limits.h for PATH_MAX definition as well.

This fixes the build on Android.
Signed-off-by: Alexey Dobriyan (SK hynix) <adobriyan@gmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/YRukaQbrgDWhiwGr@localhost.localdomainSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>