- Got rid of all the FILE* stuff in the FS code, relying on low-level

- Got rid of all the FILE* stuff in the FS code, relying on low-level
functions exclusively. It now manages its own per-file 2KB read buffers.
Writes are no longer buffered.
- Removed function "FS_Flush" and cvar "log_sync", since they're no
longer relevant
- Package's file descriptors are now duplicated when opening a new file
inside a package, to make package substitution at run time impossible on
non-Win32 systems. Added a couple of "lseek" when necessary (before
"read" calls in "FS_Read").
- Removed unused functions "FS_Eof", "Log_Print" and "S_ClearBuffer"
- Several other minor changes and fixes in the FS code
- Changed log open mode to "a" from "at" since 't' seems a Win32-only
extension

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@4946 d7cf8633-e32d-0410-b094-e92efae38249