tweak c macros per review

Author: mcspr

cores/esp8266/Arduino.h

@@ -219,9 +219,9 @@ void optimistic_yield(uint32_t interval_us);
 // undefine stdlib's definitions when encountered, provide abs that supports floating point for C code
 #ifndef __cplusplus
 #undef abs
-#define abs(x) ((x)>0?(x):-(x))
+#define abs(x) ({ __typeof__(x) _x = (x); _x > 0 ? _x : -_x; })
 #undef round
-#define round(x) ((x)>=0?(long)((x)+0.5):(long)((x)-0.5))
+#define round(x) ({ __typeof__(x) _x = (x); _x >= 0 ? (long)(_x + 0.5) : (long)(_x - 0.5); })
 #endif // ifndef __cplusplus
 
 // from this point onward, we need to configure the c++ environment