poet_math.h overrides div function in stdlib.h

[connorimes]

poet.h includes poet_math.h which specifies the div macro. If poet.h is included from another library or binary before stdlib.h, a compile error occurs:

/usr/include/stdlib.h:788:14: error: expected identifier or ‘(’ before ‘int’
 extern div_t div (int __numer, int __denom)
              ^
/usr/local/include/poet/poet_math.h:199:27: error: expected ‘)’ before ‘/’ token
 #define DB_DIV(a, b) ((a) / (b))
                           ^

Applications that use the div function from the standard library will have problems. poet.h probably should not depend on the internal poet_math.h - the real_t typedef should handled differently.