pythongh-101100: Fix datetime reference warnings (pythonGH-114661)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Author: smontanaro

Doc/conf.py

@@ -89,20 +89,25 @@
 nitpick_ignore = [
     # Standard C functions
     ('c:func', 'calloc'),
+    ('c:func', 'ctime'),
     ('c:func', 'dlopen'),
     ('c:func', 'exec'),
     ('c:func', 'fcntl'),
     ('c:func', 'fork'),
     ('c:func', 'free'),
+    ('c:func', 'gettimeofday'),
     ('c:func', 'gmtime'),
+    ('c:func', 'localeconv'),
     ('c:func', 'localtime'),
     ('c:func', 'main'),
     ('c:func', 'malloc'),
+    ('c:func', 'mktime'),
     ('c:func', 'printf'),
     ('c:func', 'realloc'),
     ('c:func', 'snprintf'),
     ('c:func', 'sprintf'),
     ('c:func', 'stat'),
+    ('c:func', 'strftime'),
     ('c:func', 'system'),
     ('c:func', 'time'),
     ('c:func', 'vsnprintf'),