UNIXFS_get_unix_path.

Accept MTCOMP as an alias for MTCOMPRESSION on those systems, having
the former, but not the latter.
Only enable operations supported by the host OS in
TAPE_CreatePartition() and TAPE_Prepare().

- Isotropic mapping mode: Adjust the viewport extension in
  SetWindowExtEx, handle negative extents.
- Support the isotropic mapping mode in the enhanced metafile driver.
- New tests.

which is useful for debugging.

writing functions.

Add a function for comparing expressions and use it to eliminate
redundant callback functions.

proxies and stubs.

UNIXFS_get_unix_path, but leave all others alone.

already have them filled in.