strftime() broken for "c" and "X" specifiers.

[bipolar]

Found while analyzing Python's test suite results for test_strptime.py.

(same results on beta4 and on hrev567104, both 64 bits)

The following minimal code:

import time

time_tuple = time.struct_time((1999,3,17,22,44,55,2,76,0))

# Specifiers' list from:
# https://pubs.opengroup.org/onlinepubs/9699919799/functions/strptime.html
for c in 'aAbBcCdDehHIjmMnprRStTUwWxXyY%':
    print('Testing "%s": "%s"' % (c, time.strftime('%' + c, time_tuple)))

prints correct values for all specifiers except for "c" and "X", as on Haiku I get:

Testing "c": ""
Testing "X": ""

For comparison, on both Win10 and Linux I get:

Testing "c": "Wed Mar 17 22:44:55 1999"
Testing "X": "22:44:55"

As far as I can tell, time.strftime() is basically just calling the system's strftime() on Haiku/Linux (and wcsftime on Win).

On the seemingly related #17884 davidkaroly said it wxWidgets was also affected and:

"most likely %c, %x, %X are impacted."

Not sure if he still sees the same there.

Seems to me that nl_strftime() is not producing correct results for D_T_FMT (%c) and T_FMT (%X), but works fine for T_FMT_AMPM (%r) and D_FMT (%x).

(That is as far as I can go :-/)