madtty: add support for relative/absolute mode (ESC[?6h, ESC[?6l)
madtty: add support for relative/absolute mode (ESC[?6h, ESC[?6l)

Based on a patch from Ross Mohn.

Signed-off-by: Marc Andre Tanner <cc7c5be316e48d137cbb549833b85d91034d799d@brain-dump.org>

delphinus35/dvtm,seanyeh/dvtm,armanbilge/dvtm,seanyeh/dvtm,delphinus35/dvtm,benjohnson2001/dvtm,raedwulf/dvtm,lotrfan/dvtm,tgvaughan/dvtm,gridsystem/dvtmx,seanyeh/dvtm,lotrfan/dvtm,medgar123/dvtm,tgvaughan/dvtm,medgar123/dvtm,tgvaughan/dvtm,raedwulf/dvtm,lotrfan/dvtm,gridsystem/dvtmx,benjohnson2001/dvtm,benjohnson2001/dvtm,raedwulf/dvtm,samaaron/dvtm,armanbilge/dvtm,medgar123/dvtm,samaaron/dvtm