Update xrdp-neutrinordp.c to support side button (forward/back) click #1609

Job	Run time
code formatting check	29s
cppcheck	7m 25s
min features with gcc	1m 0s
min features with g++	1m 14s
min features with clang	1m 8s
max features with gcc	2m 12s
max features with g++	2m 8s
max features with clang	2m 30s
max features with gcc and DEBUG	56s
max features with gcc for 32-bit arch (legacy OS)	1m 26s
max features with g++ for 32-bit arch (legacy OS)	1m 30s
max features with clang for 32-bit arch (legacy OS)	1m 31s
	23m 29s

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