AGI: use Common::String::format when possible

Use Common::String::format instead of a MAXPATHLEN-sized char[] buffer.
DRASCULA: use Common::String::format when possible

Use Common::String::format instead of a MAXPATHLEN-sized char[] buffer.
AGI: use shorter sizes for buffers

Instead of allocate them with MAXPATHLEN as size, just give them the
size for the data that are going to be written on them.
Merge pull request #552 from pinotree/reduce-maxpathlen

Reduce MAXPATHLEN usage