Make lift_gamma_gain thread-safe.
Make lift_gamma_gain thread-safe.

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