Merge cling unlocking of user code execution.

core/base/inc/TVirtualMutex.h

core/base/src/TVirtualMutex.cxx

core/metacling/src/TCling.cxx

core/metacling/src/TClingCallbacks.cxx

core/metacling/src/TClingCallbacks.h

core/thread/inc/ROOT/TReentrantRWLock.hxx

core/thread/inc/TMutex.h

core/thread/inc/TMutexImp.h

core/thread/inc/TPosixMutex.h

core/thread/src/TMutex.cxx

core/thread/src/TPosixMutex.cxx

core/thread/src/TRWMutexImp.cxx

core/thread/src/TRWMutexImp.h

core/thread/src/TReentrantRWLock.cxx

...er/cling/include/cling/Interpreter/InterpreterCallbacks.h

interpreter/cling/lib/Interpreter/EnterUserCodeRTTI.h

interpreter/cling/lib/Interpreter/IncrementalExecutor.cpp

interpreter/cling/lib/Interpreter/IncrementalExecutor.h

interpreter/cling/lib/Interpreter/Interpreter.cpp

...ter/cling/lib/Interpreter/MultiplexInterpreterCallbacks.h