Custom built FFmpeg with -framerate

avconv has a regression where the x11grab -framerate option
doesn't work - this script is the new and improved stopgap for
when avconv bug 574 is resolved
Added framerate to output codec
Remove output fps flag

Apparently, ffmpeg's x11grab device automatically handles
duplication without saying so in the output.

ffmpeg -f x11grab -framerate 60 [...] -vcodec libx264 out.avi
results in a 60fps file with 60*duration frames even if the input
is a lower framerate (IE: my system gets 40fps from x11grab, the
device will duplicate frames it misses to reach 60fps input, and
the output will naturally match the input at 60fps)
Shorter codec option format
Deprecated avconv, moved completely to ffmpeg
Remove pixel format/audio channel warnings
Get wininfo with awk
Exit normally after showing usage
Replace backticks with $()
Assign filter_v earlier so that $blind can unset it
Changed input loop to use breaks
Reordered input info in input post processing
Replaced "Created by" with github link
Updated file size estimate under scale
Added avconv deprecation warning
Modified filesize estimate

Subsequent testing shows Mb per minute to go from 230Mb up to
550Mb. I'm leaving it at "up to 700Mb/s" to be safe
Preserve quotes/escaping in remaining parameters