Remove iso646.h include from Config.h

Author: zuckschwerdt

include/SoapySDR/Config.h

@@ -48,7 +48,6 @@
   #define SOAPY_SDR_EXTERN
 #endif // SOAPY_SDR_DLL
 
-#include <iso646.h>
 
 #ifndef _MSC_VER
 #include <stdbool.h>

include/SoapySDR/Config.hpp

@@ -10,4 +10,9 @@
 
 #pragma once
 #include <SoapySDR/Config.h>
-#include <ciso646>
+
+#if (defined(_MSC_VER) || __cplusplus < 201703L)
+  // For old or nonconforming compilers,
+  // using the alternative operator representations may require including this header.
+  #include <ciso646>
+#endif