[estebanzimanyi]

pymeos_initialize sets a date style or an interval style given by name
through meos_set_datestyle and meos_set_intervalstyle, passing each the
null value its extra parameter takes in C: _ffi.NULL for the void
pointer of meos_set_datestyle and 0 for the int of
meos_set_intervalstyle. MEOS overwrites extra with the style it parses
from the name, so the value passed is never read.

tests/meos_init_test.py sets each date style and interval style by name
and reads it back with meos_get_datestyle and meos_get_intervalstyle,
restoring the styles conftest initializes after each case.