Restore LF_BACKOFF

Moved InnoDB UT_RELAX_CPU() to server. Restored cross-platform LF_BACKOFF
implementation basing on UT_RELAX_CPU().

include/atomic/generic-msvc.h

@@ -90,37 +90,7 @@ C_MODE_END
   ret= 0; /* avoid compiler warning */ \
   ret= IL_COMP_EXCHG ## S (a, ret, ret);
 #endif
-/*
-  my_yield_processor (equivalent of x86 PAUSE instruction) should be used
-  to improve performance on hyperthreaded CPUs. Intel recommends to use it in
-  spin loops also on non-HT machines to reduce power consumption (see e.g 
-  http://softwarecommunity.intel.com/articles/eng/2004.htm)
 
-  Running benchmarks for spinlocks implemented with InterlockedCompareExchange
-  and YieldProcessor shows that much better performance is achieved by calling
-  YieldProcessor in a loop - that is, yielding longer. On Intel boxes setting
-  loop count in the range 200-300 brought best results.
- */
-#ifndef YIELD_LOOPS
-#define YIELD_LOOPS 200
-#endif
-
-static __inline int my_yield_processor()
-{
-  int i;
-  for(i=0; i<YIELD_LOOPS; i++)
-  {
-#if (_MSC_VER <= 1310)
-    /* On older compilers YieldProcessor is not available, use inline assembly*/
-    __asm { rep nop }
-#else
-    YieldProcessor();
-#endif
-  }
-  return 1;
-}
-
-#define LF_BACKOFF my_yield_processor()
 #else /* cleanup */
 
 #undef IL_EXCHG_ADD32