#1 /tmp in own partition

[Julius Gehr]

crono failed while renaming /tmp_crono.3X0rpS to /etc/security/access.conf. rename(2) does not work across different mount points. Furthermore, it has not be checked if rename succeeded. This patch does:

1) introduce option TMPDIR in Makefile.defs, where a tmp-directory on the same partition as /etc can be chosen.

2) all rename()s are checked

3) deleted redundant code in void flush_loginaccess() and flush_hostsequiv()

[Julius Gehr]