Clock validate mode

[sebres]

Clock validate feature (option -valid 1|0 for validity check) re-implemented for tclclockmod, see ticket 3475995 for previous tcl'ed variant.

Tenor

• clock scan get an new option -validate 0|1 in order to control validity of the scanned date-time (for both methods: format-scan and free-scan). Example:

% clock scan "30 February 2018"
1519945200
% clock scan "30 February 2018" -valid 1
unable to convert input string: invalid day

• additionally provided an opportunity to choice the default validity mode (general interpreter option via clock configure -validate 1);
• completely re-implemented in C (many times faster as the tcl'ed variant, so the execution overhead by -valid on is almost to neglect);
• backwards compatible to the original tcl-clock ensemble (currently -valid off used as default mode);
• test-cases are extended in order to cover both valid-modes.

Summary

If valid mode used, the scans of "not valid" date-time (like in the tests clock-11.x) or similar like 30 February cause an error:

% clock configure -valid 1; #default validate is on for this interpreter

% clock scan 01010021970 -format %d%m%j%Y -gmt 1
unable to convert date-time string "01010021970": invalid julian day
% clock format [clock scan "2008-02-30"] -format "%Y-%m-%d"
unable to convert date-time string "2008-02-30": invalid day
% clock format [clock scan "24:62:80"] -format "%T"
unable to convert date-time string "24:62:80": invalid time

% clock configure -valid 0; # the same without validate...

% clock scan 01010021970 -format %d%m%j%Y -gmt 1
0
% clock format [clock scan "2008-02-30" -valid 0] -format "%Y-%m-%d"
2008-03-01
% clock format [clock scan "24:62:80" -valid 0] -format "%T"
23:59:59