[Summary] Fixed audio export on Windows. Added support of windows platform for the function that calculated hardware concurrency.

Because there was no implementation for this function on windows it used to return 0. This meant that no thread was created to process the data.

libs/pbd/cpus.cc

@@ -28,6 +28,8 @@
 #include <stddef.h>
 #include <sys/types.h>
 #include <sys/sysctl.h>
+#elif defined(PLATFORM_WINDOWS)
+#include <Windows.h>
 #endif
 
 #include "pbd/cpus.h"
@@ -48,6 +50,10 @@ hardware_concurrency()
 #elif defined(HAVE_UNISTD) && defined(_SC_NPROCESSORS_ONLN)
         int const count=sysconf(_SC_NPROCESSORS_ONLN);
         return (count>0)?count:0;
+#elif defined(PLATFORM_WINDOWS)
+		SYSTEM_INFO sys_info;
+		GetSystemInfo( &sys_info );
+		return sys_info.dwNumberOfProcessors;
 #else
         return 0;
 #endif