Fix Win32 <ziparchive/zip_archive.h>.

Contrary to the comment in AndroidConfig.h, mingw does have
__BEGIN_DECLS and __END_DECLS; you just have to #include <sys/cdefs.h>
first. Which is strictly true normally too, but you're going to
get it transitively with bionic or glibc.

Change-Id: I2f2de45f56a7217f91df322d8e896280997ae7a0