_XawTextSelectionList should use XInternAtoms

https://gitlab.freedesktop.org/xorg/lib/libxaw/-/blob/master/src/Text.c#L3104-3125

The _XawTextSelectionList() function loops over a list of atoms, calling XInternAtom() on each one at a time, causing an X server round trip for each one. It should call XInternAtoms() instead to batch the whole list into a single X server round trip.