Changes

* [[SY6845EA]] by Synertek

* [[F68B45P]] by Freescale

* CRTC6545 (MOS, Rockwell, Synertek) is pin-compatible with the 6845 and only has minor differences

* [https://github.com/hoglet67/BeebFpga/blob/dev/src/common/mc6845.vhd BeebFpga] [https://github.com/MiSTer-devel/Amstrad_MiSTer/blob/master/rtl/UM6845R.v MiSTer] [https://opencores.org/websvn/filedetails?repname=System09&path=%2FSystem09%2Ftrunk%2Frtl%2FVHDL%2Fcrtc6845.vhd OpenCores] Verilog/VHDL implementations of the 6845