Reintroduced dosemu_proc_self_exe, as it comes in really handy for dosdebug.
Fall back to dosemu_argv[0] for older valgrinds and qemu if it's NULL.
Plugged a small memory leak.


git-svn-id: https://dosemu.svn.sourceforge.net/svnroot/dosemu/trunk@1192 7758b857-130e-0410-ab9c-d8735a528d18