Adds Arduino standard macro-functions (espressif#6726)

* Adds Arduino standard functions

* Fixes round()

Adds Arduino basic math Macros with '_' prefix.

Author: SuGlider

Diff for: cores/esp32/Arduino.h

@@ -69,7 +69,12 @@
 #define __STRINGIFY(a) #a
 #endif
 
+// can't define max() / min() because of conflicts with C++
+#define _min(a,b) ((a)<(b)?(a):(b))  
+#define _max(a,b) ((a)>(b)?(a):(b))
+#define _abs(x) ((x)>0?(x):-(x))  // abs() comes from STL
 #define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
+#define _round(x)     ((x)>=0?(long)((x)+0.5):(long)((x)-0.5))  // round() comes from STL
 #define radians(deg) ((deg)*DEG_TO_RAD)
 #define degrees(rad) ((rad)*RAD_TO_DEG)
 #define sq(x) ((x)*(x))
@@ -89,6 +94,7 @@
 #define bitRead(value, bit) (((value) >> (bit)) & 0x01)
 #define bitSet(value, bit) ((value) |= (1UL << (bit)))
 #define bitClear(value, bit) ((value) &= ~(1UL << (bit)))
+#define bitToggle(value, bit) ((value) ^= (1UL << (bit)))
 #define bitWrite(value, bit, bitvalue) ((bitvalue) ? bitSet(value, bit) : bitClear(value, bit))
 
 // avr-libc defines _NOP() since 1.6.2
@@ -168,12 +174,13 @@ void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t val);
 #include "Esp.h"
 #include "esp32/spiram.h"
 
+// Use float-compatible stl abs() and round(), we don't use Arduino macros to avoid issues with the C++ libraries
 using std::abs;
 using std::isinf;
 using std::isnan;
 using std::max;
 using std::min;
-using ::round;
+using std::round;
 
 uint16_t makeWord(uint16_t w);
 uint16_t makeWord(uint8_t h, uint8_t l);
@@ -203,9 +210,6 @@ void noTone(uint8_t _pin);
 long random(long);
 #endif /* __cplusplus */
 
-#define _min(a,b) ((a)<(b)?(a):(b))
-#define _max(a,b) ((a)>(b)?(a):(b))
-
 #include "pins_arduino.h"
 
 #endif /* _ESP32_CORE_ARDUINO_H_ */