Switch off line wrapping in case dots occupy extra line

This commit uses the (hopefully) standard rmam and smam escape sequences
which toggle off and on line wrapping respectively.

This is so that extra dots that don't fit the current line won't be
displayed in the next line, which would in turn make the shell
display a new prompt on the next line after the dots are hidden.

I've added a check for $terminfo rmam and smam values to be sure we have
them before printing them out.

If this commit breaks something post an issue with your terminal
emulator and $TERM value and we'll figure out what went wrong.