Update DOSBox master to r3858

Your DOSBox repository is at r3798. This updates it to r3858. This is simply content from DOSBox SVN, without any changes.

The repository moved to http://svn.code.sf.net/p/dosbox/code-0 plus the UUID changed. I used rewriteUUID plus the procedure described at https://git.wiki.kernel.org/index.php/GitSvnSwitch. (There is also rewriteRoot, but it can't be used together with rewriteUUID.) I also had to do some tricky things to re-generate the git svn metadata because I didn't get it from GitHub. Then I simply got new revisions via `git svn rebase`.

If you still have the git svn metadata, you could easily update the repository yourself instead of using this pull request.