Make CONTROL + DELETE delete a line

If CONTROL + INSERT inserts a line then it seems natural CONTROL + DELETE
removes a line.
Make Shift+Home equal to CLS in ascii mode
Remove duplicated code in strhandle

The error condition was duplicated in two different switches.
This new version centralized the error handling in only one place.
Remove non defined behaviour in selcopy

It is not defined when lateral effects of expressions are
calculated, so an expression as:

	--last >= gp && !(selected(last - gp, y)

is non portable.
Removing the w3img support.

The patch to add w3img support destroys our way to handle fps and so stop
wasting resources on fast scrolling. Due to w3img being a hack to display
images in an ugly way, is there no need to support this. Use some real way to
display images.
Merge remote-tracking branch 'origin/master'