This allows perfect display on CRT
The work is based on https://github.com/antonioginer/switchres which is the switchres code extracted from GroovyMAME and made available to other emulators that wish to add CRT display.
This first commit simply concerns linux using the SDL2 video backend.
Add INCLUDE_SWITCHRES=1 to enable switchres functionnality at make.
To test under Linux you need:
* a valid switchres.ini in /etc
* libswitchres.so in your LD_LIBRARY_PATH