add support for simple character input via the system console

add support for simple character input via the system console

dev/alpha_access.h:
    -  use our standard types instead of this extra typedef
    -  advance the ALPHA_ACCESS version since the interface
    has changed.  *this means you need a new console binary*
    -  shuffle a couple things around to pack the data structure
    a bit better
    -  add a placeholder for character input
dev/alpha_console.cc:
    Clean up the read code path a bit and add support for character
    input via the console

    Clean up the write path and use a switch instead of a bunch of
    if statements

--HG--
extra : convert_revision : a1a5bc8fed9ec9c4c46548fdf79604661668b81a