Modernization and clean-up (login-tool, 8790dd9)

Created 12/5/2007, updated 3/5/2024

Various clean-ups which don't alter the compiled code but improve the source:

change date format in header for consistency with other projects - remove Subversion buzz - update and normalize copyright - rewrap to 132-columns for better readability - improve alignment for better readability - use C99 for loops - whitespace fixes (trailing whitespace, missing newline at end of file) - use EXIT_SUCCESS rather than 0

Signed-off-by: Greg Hurrell <greg@hurrell.net>