Expand on time zone issues in "Outsourced".

* tz-art.htm: The joke in the "Outsourced" episode may correctly exploit
the time difference between New York and San Francisco, but meanwhile,
they got the corresponding time in Mumbai totally wrong.
Simplify Pakistan and Mont rules, fix Dhaka rule.

* asia (Dhaka): Replace 23:59 with 24:00 to align match supporting
commentary, now that zic can handle it.
(Pakistan): Merge two rules that can be covered as one.
* northamerica (Mont): Simplify rules per existing commentary, since zic
has been able to handle this since 1998.
* NEWS: Document this.
More consistent spacing in UNTIL fields.

* zic.8: Also fix this in the Zone line example.
Avoid bracketing links when alone on a line.
Commentary fixes, mostly 80-column issues.
Don't put spaces before tabs.

* Makefile (check_tabs): New rule.
(check): Use it.
Also, fix all other files to not have spaces before tabs.