abs() and labs()

Use the corresponding macro M_ABS defined in stdlib.h instead of calling abs() and absl() in the stdlib:

  /* extract

  /* macro definitions of abs() and labs() */

  #define M_ABS(j)  (((j) >= 0) ? (j) : -(j))

  extern int     abs(int j);

  extern long int labs(long int j);

But be careful as M_ABS() is a macro,

  i = M_ABS(j++);

and is not the same as:

i = abs(j++);