fixed testbench and st_xsq to match expecting xsq values. also added

libraries/base/common/src/vhdl/common_math_pkg.vhd

libraries/dsp/st/hdllib.cfg

libraries/dsp/st/src/vhdl/st_pkg.vhd

libraries/dsp/st/src/vhdl/st_xsq.vhd

libraries/dsp/st/tb/vhdl/tb_st_xsq.vhd

libraries/dsp/st/tb/vhdl/tb_tb_st_xsq.vhd