Update version to Custom-v11.3 #1338

Job	Run time
build (base)	6m 5s
build (clang)	7m 17s
build-gcc-heli	6m 13s
autotest-heli (sitltest-heli)	9m 23s
autotest (sitltest-copter-tests1a)	14m 22s
autotest (sitltest-copter-tests1b)	14m 20s
autotest (sitltest-copter-tests1c)	16m 48s
autotest (sitltest-copter-tests1d)	16m 29s
autotest (sitltest-copter-tests1e)	15m 48s
autotest (sitltest-copter-tests2a)	14m 6s
autotest (sitltest-copter-tests2b)	31m 56s
	2h 32m 47s

Provide feedback