Bilinear filler value corrected when matrix size is odd.

[zhengwy888]

I believe there was an typo in BilinearFiller.
E.g. if you set the kernel size to be 3. the filler produces the following result:

0.062500 0.187500 0.187500 
0.187500 0.562500 0.562500 
0.187500 0.562500 0.562500

Where it should have been

0.250000 0.500000 0.250000 
0.500000 1.000000 0.500000 
0.250000 0.500000 0.250000 

Looking at the code and this is because the matrix size condition (f%2) should have used the actual matrix size.

Let me know what you think.

[Noiredd]

Fixed in #5713.