Latest official MiSTer FPGA core updates

The following are the latest core updates for official MiSTer FPGA releases.

PCXT:
* Adjust RAM data output timing.
* Measures against 601 errors in turbo mode.
* Added 8259A INT signal output delay.

All changes by @kitune-san

Main:
– input: update to support more input devices (Martin Donlon, Javier Rodas).
– input: Make key/Button remap permanent.
– input: improved dialogs.
– MGL: support for absolute paths (must be started from / ).
– Fix some IDE emulation problems (zakk4223).
– N64 loading improvements (Marcoen Hirschberg).
– Improved handling of boot.rom and persistent file loading.
– Some other fixes and tweaks.

MegaDrive:
– Implement EEPROM saves
– Add SF-001/002/004, Realtec mappers.
– Support for some ROMs with special checks.
– Fix save LED activity.
– Adjust PSG level and filtering.
– Updates from Nuked team.
– Other fixes and tweaks.