QCD part 1, define M_PI if not defined

qcd/part_1/src/random.c

@@ -4,6 +4,10 @@
 
 /* 64 bit MT PRNG from mt19937-64.c */
 #define NN 312
+#ifndef M_PI
+    #define M_PI 3.14159265358979323846
+#endif
+
 extern int mti;
 extern unsigned long long mt[NN];
 void init_genrand64(unsigned long long seed);