tests/tiny_ssim: replace #define by typedef

See e.g https://stackoverflow.com/questions/1666353/are-typedef-and-define-the-same-in-c
for rationale.
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Reviewed-by: Hendrik Leppkes <h.leppkes@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>

tests/tiny_ssim.c

@@ -79,11 +79,11 @@ static float ssim_end1( int s1, int s2, int ss, int s12 )
  * s1*s1, s2*s2, and s1*s2 also obtain this value for edge cases: ((2^10-1)*16*4)^2 = 4286582784.
  * Maximum value for 9-bit is: ss*64 = (2^9-1)^2*16*4*64 = 1069551616, which will not overflow. */
 #if BIT_DEPTH > 9
-#define type float
+    typedef float type;
     static const float ssim_c1 = .01*.01*PIXEL_MAX*PIXEL_MAX*64;
     static const float ssim_c2 = .03*.03*PIXEL_MAX*PIXEL_MAX*64*63;
 #else
-#define type int
+    typedef int type;
     static const int ssim_c1 = (int)(.01*.01*PIXEL_MAX*PIXEL_MAX*64 + .5);
     static const int ssim_c2 = (int)(.03*.03*PIXEL_MAX*PIXEL_MAX*64*63 + .5);
 #endif
@@ -95,7 +95,6 @@ static float ssim_end1( int s1, int s2, int ss, int s12 )
     type covar = fs12*64 - fs1*fs2;
     return (float)(2*fs1*fs2 + ssim_c1) * (float)(2*covar + ssim_c2)
          / ((float)(fs1*fs1 + fs2*fs2 + ssim_c1) * (float)(vars + ssim_c2));
-#undef type
 }
 
 static float ssim_end4( int sum0[5][4], int sum1[5][4], int width )