0029935: Foundation Classes - introduce OSD_ThreadPool class defining a thread pool

New class OSD_ThreadPool has been introduced to define a Thread Pool for multi-threading algorithm.
Thread Pool assigns a serial number for each thread allowing Multi-Threading algorithm to allocate thread-local storage variables as an array whose size is the same as the number of threads.

OSD_ThreadPool also redirects exceptions to a thread calling parallel execution and consistently initializes FPE exception handling.

New class Standard_Condition provides a platform-independent  tool similar to Event in WinAPI.

A new auxiliary function Standard_Atomic_CompareAndSwap() has been introduced
for performing atomic compare and swap of integer number.
Standard_Atomic_Increment/Standard_Atomic_Decrement fallback implementation
using ASM code for x86 processors for GCC has been dropped;
instead, it is expected that GCC should be properly configured targeting modern x86 architectures.

OSD_Signal now declares fFltExceptions as thread_local variable accessible through OSD::ToCatchFloatingSignals() property.
Standard_THREADLOCAL macro (wrapping thread_local attribute) has been moved to public header Standard_Macro.hxx.

OSD_Parallel::ForEach() has been extended with new optional parameter theNbItems and uses OSD_ThreadPool::DefaultPool().

src/OSD/OSD.hxx

@@ -104,7 +104,10 @@ public:
   //! user's code. Refer to Foundation Classes User's Guide for further details.
   //!
   Standard_EXPORT static void SetSignal (const Standard_Boolean theFloatingSignal = Standard_True);
-  
+
+  //! Return floating signal catching value previously set by SetSignal().
+  Standard_EXPORT static Standard_Boolean ToCatchFloatingSignals();
+
   //! Commands the process to sleep for a number of seconds.
   Standard_EXPORT static void SecSleep (const Standard_Integer aDelay);