normalize non-integer frame rates for Matroska
normalize non-integer frame rates for Matroska

Maybe this should be done for other or all formats. After all, fps
reduced to a certain level of precision is equivalent to the broadcast
standard frame rate. However, Matroska and WebM are both extremely
common and known to not directly store the frame rate.

j-b-m/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,mltframework/mlt