v7.11 release

7.11 Released 1/7/2019

• Queue:GetWithDefault() methods that
  take a default-value argument (by-reference)
  now return their return-value by-value rather
  than by-reference, to avoid any possibility
  of returning a dangling reference if they
  are called with a temporary-object argument.
• Hashtable:Get*WithDefault() methods that
  take a default-value argument (by-reference)
  now return their return-value by-value rather
  than by-reference, to avoid any possibility
  of returning a dangling reference if they
  are called with a temporary-object argument.
• _MSC_VER was misspelled as MSC_VER in
  PseudoFlattenable.h, causing the code to
  fail to compile under MSVC2013. Fixed.
• Fixed a bug in Mutex.h that would prevent
  MUSCLE_QT_HAS_THREADS from being correctly
  #defined if MUSCLE_AVOID_CPLUSPLUS11 wasn't set.
• Fixed FileDescriptorDataIO.h to compile
  correctly under Windows in the case where it
  is the first muscle-include file to be parsed.
• MuscleSupport.h now checks for the presence of
  _WIN32 (in addition to __WIN32__, etc)
• Fixed an assertion failure that could be
  triggered inside DeadlockFinder_ProcessEnding()
  if MUSCLE_ENABLE_DEADLOCK_FINDER was defined.
• Fixed some warnings generated by clang++ when
  -Wshadow is specified on the compile line.