ffmpeg: setup jni on load

Allows to make use of ffmpeg MediaCodec hardware accelerators.
This patch requires ffmpeg to be built with the JNI module
(see related patch in the daemon).

Change-Id: If6454a5f27f895ef14ba8d378bae7c29ed87c8ad
Reviewed-by: Hadrien De Sousa <hadrien.desousa@savoirfairelinux.com>

build-daemon.sh

@@ -274,6 +274,7 @@ mkdir -p ${LIBRING_JNI_DIR}
 ${NDK_TOOLCHAIN_PATH}/clang++ --shared -Wall -Wextra  ${ANDROID_APP_DIR}/libringclient/src/main/jni/ring_wrapper.cpp \
                                         ${RING_BUILD_DIR}/src/.libs/libring.a \
                                         -static-libstdc++ \
+                                        -I${RING_SRC_DIR}/contrib/${TARGET_TUPLE}/include \
                                         -I${RING_SRC_DIR}/src -L${RING_SRC_DIR}/contrib/${TARGET_TUPLE}/lib \
                                         ${STRIP_ARG} --std=c++11 \
                                         ${STATIC_LIBS_ALL} \

ring-android/libringclient/src/main/jni/ringservice.c.template

 #include "logger.h"
+extern "C" {
+#include "libavcodec/jni.h"
+}
 
 JavaVM *gJavaVM;
 const char *kringservicePath = "cx/ring/daemon/RingserviceJNI";
@@ -18,6 +21,10 @@ JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved) {
 
     RING_INFO("JNI_OnLoad");
 
+	if (av_jni_set_java_vm(vm, reserved)) {
+        RING_ERR("JNI_OnLoad: av_jni_set_java_vm failed");
+	}
+
 	//Assume it is c++
 	r = vm->GetEnv ((void **) &env, JNI_VERSION_1_6);
     if (r != JNI_OK) {