re PR java/18278 (JNI functions cannot return a weak reference)

re PR java/18278 (JNI functions cannot return a weak reference)

gcc/java:
	PR java/18278:
	* expr.c (build_jni_stub): Unwrap the return value.
	* java-tree.h (soft_unwrapjni_node): New define.
	(enum java_tree_index): Added JTI_SOFT_UNWRAPJNI_NODE.
	* decl.c (java_init_decl_processing): Initialize
	soft_unwrapjni_node.
libjava:
	PR java/18278:
	* testsuite/libjava.jni/pr18278.out: New file.
	* testsuite/libjava.jni/pr18278.c: New file.
	* testsuite/libjava.jni/pr18278.java: New file.
	* include/jvm.h (_Jv_UnwrapJNIweakReference): Declare.
	* jni.cc (_Jv_UnwrapJNIweakReference): New function.
	(call): Unwrap return value if needed.

From-SVN: r107676