clean up g_date_time_get_week_day()
clean up g_date_time_get_week_day()

No functionality changes here.

Vastly simplify the algorithm for calculating the day of the week.

Fix the documentation (which is incorrectly stating that 1 means
Sunday) and clarify that the number we return is in line with ISO 8601
week day numbering.

ieei/glib-old-android,dicer/android_external_glib,ieei/glib-old-android,dicer/android_external_glib,dicer/android_external_glib,dicer/android_external_glib,ieei/glib-old-android,ieei/glib-old-android,dicer/android_external_glib