Add CPU "pause" intrinsic for MSVC

configure.ac

@@ -218,6 +218,15 @@ dnl CPU-specific settings.
 CPU_SPINWAIT=""
 case "${host_cpu}" in
   i686|x86_64)
+	if test "x${je_cv_msvc}" = "xyes" ; then
+	    AC_CACHE_VAL([je_cv_pause_msvc],
+	      [JE_COMPILABLE([pause instruction MSVC], [],
+					[[_mm_pause(); return 0;]],
+					[je_cv_pause_msvc])])
+	    if test "x${je_cv_pause_msvc}" = "xyes" ; then
+		CPU_SPINWAIT='_mm_pause()'
+	    fi
+	else
 	    AC_CACHE_VAL([je_cv_pause],
 	      [JE_COMPILABLE([pause instruction], [],
 					[[__asm__ volatile("pause"); return 0;]],
@@ -225,6 +234,7 @@ case "${host_cpu}" in
 	    if test "x${je_cv_pause}" = "xyes" ; then
 		CPU_SPINWAIT='__asm__ volatile("pause")'
 	    fi
+	fi
 	;;
   powerpc)
 	AC_DEFINE_UNQUOTED([HAVE_ALTIVEC], [ ])