xml/GenCode - Expand memory limit

xml/GenCode - Expand memory limit

GenCode processes translations in all locales.  Loading all locales is
memory-intensive (est ~20mb per locale based on `memory_get_usage()`).

The locales are tracked in `CRM_Core_I18n::singleton()`.  The behavior is
actually good for typical usage (1-2 locales per page-view), but it breaks
down when one request needs to work with all locales.  If it mattered more,
we'd probably implement some cache-management to deallocate older/unused
locales.  But for GenCode, it's OK to bump up memory requirements as high as
1gb.