options: remove --panscanrange option

This option allowed you to extend the range of the panscan controls, so
that you could essentially use it to scale the video. This will be
replaced by a separate option to set the zoom factor directly.
video: make it possible to scale/pan the video by arbitrary amounts

Add --video-align-x/y, --video-pan-x/y, --video-scale options and
properties. See the additions to the manpage for description and
semantics.

These transformations are intentionally done on top of panscan. Unlike
the (now removed) --panscanrange option, this doesn't affect the default
panscan behavior. (Although panscan itself becomes kind of useless if
the new options are used.)
m_option: rename struct member named "new"

Cosmetic change to allow C++ code to include this header.

See github issue #195.