osd/modules/input, emu/inpttype.cpp: Made most default joystick
assignments supplied by input modules. Input modules take available
controls into consideration when generating default assignments.
emu/inpttype.ipp: Added a separate "Back" UI input separate from Cancel.
You may want an easier to hit combination for moving to the previous
menu than for exiting or cancelling input. They both default to Escape.
emu/inpttype.ipp: Added a UI Help control. Currently only used by
analog inputs menu
emu/inpttype.h: Moved I/O port field type enum to its own header and
sorted UI controls so they appear in a more logical order.
ui: Don't use UI Select to restore defaults - people should be getting
used to the UI Clear input by now. UI Select cycles multi-value items
instead.
ui/inputmap.cpp: Don't use immediate cancel to cycle between clearing
and restoring default assignment (use UI Clear instead).
osd: Reduced the number of files needing to include the dreaded emu.h.
Got some implementation out of headers.
Since asteroid overrides the default input assignments, slikstik.cfg
needs to use the syntax for overriding specific inputs. There was also
a bug in how specific input overrides are applied.
