checkchessboard.cpp + planardetect.cpp:  inverse multiplication a/b == a*(1/b), (retry merge)
Revert "checkchessboard.cpp + planardetect.cpp:  inverse multiplication a/b == a*(1/b), (retry merge)"

This reverts commit 40290dfc5cf41525dfca7a14402c85ab9fcac5ae.
Revert "bgfg_gaussmix.cpp: const pointer and parameter, FPU optimization"

This reverts commit e87adf2e9a0032ae458d5270568954023719767d.
ccb + pd (again)