no need for libm or GSL to compile the interpolate code

tools/spin/interpolate_gneb/README

@@ -2,7 +2,7 @@ Interpolate.x tries to perform a cubic polynomial interpolation
 of the MEP.  
 
 Compile the program with:
-gcc interpolate.c -o interpolate.x -lm -lgsl
+gcc interpolate.c -o interpolate.x
 
 and then run it as:
 ./interpolate.x

tools/spin/interpolate_gneb/interpolate.c

@@ -9,8 +9,6 @@
 ------------------------------------------------------------------------- */
 
 #include <stdio.h>
-#include <math.h>
-#include <time.h>
 #include <string.h>
 #include <stdlib.h>