readium-sdk : update submodule to 8fdbfd7

summary of changes from ‘git submodule summary’

* readium-sdk f76c31a...8fdbfd7 (13):
  > Merge pull request #55 from datalogics-bhaugen/jenkins-build-android
  > Fixed issue related to JNI static jclass pointer initialisation (ERROR "accessed stale local reference"), observable in Android ICS+ (>= Ice Cream Sandwich 4.0) because of the new garbage collector which moves memory allocations. This was needed on my KitKat device despite targetSDKVersion set to 11 in project properties (which should normally ensure JNI compatibility mode with post-4.0 garbage collection ... I'm not sure why the compatibility mode did not kick-in though, I observed this bug in both Dalvik and ART runtimes). Future uses of the jni::Class wrapper (defined in jni_class.h) should be double-checked, to ensure that the initialisation macro from helpers.h is used to create the correct persistent jclass memory pointer! (behind the scenes: (jclass)env->NewGlobalRef(tmpPtr)). Perhaps INIT_CLASS_RETVAL() should be called directly inside the jni::Class constructor that takes a string parameter (the class qualified name, used to lookup via end->FindClass()). This would make the API transparent to the JNI garbage collection subtleties?
  > BUG 74: Added some more logging to help verify paths
  > Remove unneeded file
  > added flow froperties to the split properties lookup table
  > Updates to RDSpineItem to bring in line with the version used by the OS X launcher.
  > Update copyright strings for RDServices classes.
  > Merge branch 'develop' into feature/rdservices-apple
  > Bring over another change from SDKLauncher-iOS develop (from April 14).
  > Small change to previous commit.
  > Bring over recent additions from SDKLauncher-iOS develop, which isn't using RDServices from readium-sdk yet.
  > Merge branch 'develop' into feature/rdservices-apple
  > Initial commit of RDServices classes for Apple platform.