M_PI_4 and M_PI_2 added (not provided by avr-gcc)

sw/include/std.h

@@ -40,6 +40,14 @@ typedef uint8_t bool_t;
 /* Unit (void) values */
 typedef uint8_t unit_t;
 
+#ifndef M_PI_4
+#define M_PI_4 (M_PI/4)
+#endif
+
+#ifndef M_PI_2
+#define M_PI_2 (M_PI/2)
+#endif
+
 #ifndef cbi
 #define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
 #endif