bind/java: fix build on NDK r16
bind/java: fix build on NDK r16

Import <string.h> to provide a memcpy declaration.

Fixes golang/go#22766

Change-Id: I0762a1bb9d8d30bb1ae6f1a98648795ea57b0913
Reviewed-on: https://go-review.googlesource.com/79499
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/mobile,golang/mobile,golang/mobile,golang/mobile