make MOD inline

now linker doesn't complain about multiple definitions

src/base.hpp

@@ -31,7 +31,7 @@ static const int message_buffer_length = 1024;
 static char debug_message_buffer[message_buffer_length];
 extern int myrank, nprocs;
 
-int MOD(int a, int n)
+inline int MOD(int a, int n)
 {
     return ((a%n) + n) % n;
 }