Clang 3.2 requires all class members to be used in the code; this patch either removes class members that are not used or adds NS_UNUSED/NS_UNUSED_GLOBAL around them. Thanks to Andrey Mazo and Tommaso Pecorella for review.
This means removing unused private variables in random-variable-stream.{cc,h} and system-thread.h and fixing removing bad static_casts in calendar-scheduler.cc.