Merge branch 'terminal-abstraction' into 'master'

exec/load/cga_defs.js

exec/xbimage.js

src/sbbs3/ansi_parser.cpp

src/sbbs3/ansi_parser.h

src/sbbs3/ansi_terminal.cpp

src/sbbs3/ansi_terminal.h

src/sbbs3/ansiterm.cpp

src/sbbs3/answer.cpp

src/sbbs3/atcodes.cpp

src/sbbs3/bat_xfer.cpp

src/sbbs3/bulkmail.cpp

src/sbbs3/chat.cpp

src/sbbs3/chk_ar.cpp

src/sbbs3/con_hi.cpp

src/sbbs3/con_out.cpp

src/sbbs3/data.cpp

src/sbbs3/download.cpp

src/sbbs3/exec.cpp

src/sbbs3/execfile.cpp

src/sbbs3/execmsg.cpp