upd7810: remove gamemaster hack for INTFE1

The extended timer has been properly implemented in upd7810.
Tested with Continental Galaxy 2020.
upd7810: treat NMI like other interrupts
upd7810: correctly deal with external interrupts
upd7810: return meaningful value when PC3 is in control mode

When PC3 is in control mode, it acts as INT2 and external Timer Input.
INT2 may be set by connected devices through set_input_line(), so its
value can be used when reading or writing to PC3. There is currently
no code to support external timer input.
dvk_ksm: DEC VT52-compatible video terminal
(mess) num9rev: add number 9 revolution 512x32 [Carl]
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Only the demo programs tested for now
(MESS) softlist: Added new lists for Sord M5 and PTC SOL-20 cassettes. [Riley110]
(MESS) softlist: Added info in many Eastern Europe computer softlists. [Riley110]

also, renamed a few lists for consistency.
Merge pull request #33 from ramiropolla/upd7810

upd7810: interrupt-related fixes
Merge pull request #34 from shattered/_664d68d

dvk_ksm: DEC VT52-compatible video terminal
MT 03590 [Alex Jackson]
added simon skillswitch, thanks to Simon from http://www.waitingforfriday.com for making a wiring diagram
get rid of old printfs
Experiments in PCI land [O. Galibert]
Compile fix (nw)
Allow sound output if 8253 is never programmed, i.e. all output is done by modulating speaker output line.
Merge pull request #35 from shattered/_dcd0ca6

Allow sound output if 8253 is never programmed, i.e. all output is done ...
k007121.c: improve documentation (nw)
(MESS) victor9k: Floppy WIP. (nw)
redo merlin layout
twin16: note about fround (nw)