Fix typo bug in the calculation of some derivatives (dmxdt, dmydt, dmxdr, dmydr) in cvProjectPoints2 function.

Add bib reference for overall hitrate and false alarm rate for the train cascade user guide (OpenCV 2.4).

to fix difference with CUDA 8.0 results

AutoBuffer::allocate(nsz) didn't work properly when
(sz < nsz < fixed_size). In this case sz remained unchanged.

Added missing SimpleBlobDetector parameters to features2d_init.cpp.

Some CMake 3.x (2.8.12.2 is fine) provides broken build configurations
with following build error message:
    ld: fatal error: -soname: must take a non-empty argument

Linker command line sample contains this:
"-shared -Wl,-soname, -o"

The number of gaussians involved in a mixture is supposed
to be dynamically adjusted. After being increased, the number
of gaussians can't be reduced anymore.

It seems to be a regression as the legacy code
located in modules/legacy/src/bgfg_gaussmix.cpp allows to reduce
such number of gaussians.