hdl/modules/dsp_cores_pkg.vhd: constraint string

Modelsim issues an error when using an unconstrained
string type in case statements. So, we contraint it
to a suitable size.
Created wishbonized version of concordic. Tested for basic function.
Created a FTFW decoupled output FIFO component. This component aims to
help the intermediate metadata FIFO in wishbone-stream.
Added initial value for pipeline to avoid undefined values in simulation.
Created simple-wrapper, a wrapper to help converting simple blocks to
wishbone stream.
Improvements in wishbone-stream cordic.
Converted mixer to wishbone stream interface.
Synthesis test for wishbone stream.