e2fsprogs: create com_err.h link in includedir

e2fsprogs: create com_err.h link in includedir

After debian bug #192277, debian/rules started making a symlink
to com_err.h in /usr/include.  Now I have Fedora bug #550889
for the same issue, and perhaps it's time to make this link
by default, rather than fixing it up in packaging steps?

[ Changed by tytso to remove the explicit -s option; this will default
  to creating a hard link by default, which slightly faster.  If
  people want to use symlinks for all links during the install
  process, they can use configure option --enable-symlink-install.
  The reason for this change is that some file systems, like AFS,
  don't support symlinks, and AFS users complain when they can't build
  or install into AFS.  So I don't want to use symlinks
  unconditionally without a way of switching things back and forth,
  and it's easier if we just make all links made during the install
  process to be hard links or sym links. ]

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>