REQ: centerprint extensions

[molgrum]

Please add these for compatibility with FTE centerprint extensions in cspree:

/. = terminate parsing of header symbols
/P = persists with a background, clears top-align
/W = typewriter style, writing text out character by character
/S = persistent (stay!)
/M = mask (background, for a temporary /P)
/O = obituary, shows 2/3rds of the top
/B /T /L /R = bottom/top/left/right alignment
/F? = override intermission (so you can finally cancel intermission after it began - the ? should be R, I, S, F, or f, to specify the intermission mode you want)
/Ifoobar: = specifies to use 'foobar' as a title image

Thanks!