Implement new build/install mechanism
Move tmp file mgt to sf_tmp.sh. Deprecate sf_get_tmp (replaced by sf_tmpfile/sf_tmpdir). Add automatic removal of tmp files at exit.
Add sf_find_posix_shell function
sysfunc.sh: Adapt to new build system. Add /sbin to PATH.
sf_check_copy & sf_check_block: Use new tmpfile system (cleaner).
Use new build system to display software version. Add sf_finish function.
sf_msg.sh: Add sf_newline(), sf_separator(), sf_show_errors(), sf_error_count(). New system to store error messages and display them when needed.