Consequences of missing dict smart pointer

[sebres]

Because the dict-primitives are not public available (for usage in module), I've simulated the smart dict reference with simple duplication (to guarantee single reference of the object, to get alterable dict collection).

This workaround has following consequences:

• Certain objects "leakage", because each format-object (no matter localized format or not) will be stored in ::tcl::clock::LocaleFormats cache. This is very annoying especially if many dynamically formats are used;
• Certain performance degradation (for above-mentioned reason with localization of each format and duplication instead of smart-ref);
• Not optimal usage of internal cache structures by date-time conversion with fast switch of locale / formats;
• also the internal GC for the formats is not really usable (because all objects are still referenced in LocaleFormats).

All that is a reason enough to re-implement a "technical" dict smart pointer in tclclockmod, similar to clock-speedup branch in the fossil-repo of tcl-core.

The code example to reproduce a "leak" using simple dynamic clock-format:

time {
  clock format 0 -format "[expr {int(rand()*10000)}] %a %b, %x-%X" \
    -locale [lindex {en de fr} [expr {int(rand()*3)}]]
} 100000

BTW. Please note that the amount of the "leakage" of default clock ensemble is many times larger in this case (because of the format-caching).

Engine	Memory usage (x86)	Memory usage (x64)
tcl8.6-clock	ca. 130MB	ca. 170MB
tclclockmod	ca. 20MB	ca. 50MB

But nevertheless I see the necessity to "fix" it in tclclockmod.