set module variable g_ctx_name to "LMDZ"
wxios_init(): remove call to wxios_context_init
wxios_context_init(): call xios_context_initialize with COMM_LMDZ_PHY
add routine wxios_set_context() to get handle and set context to XIOS
wxios_domain_param(): change arguments and generate the domain in-place
add wxios_domain_param_unstructured(): generate domain for unstructured case
NB: access is via "domain group" (whereas it is via "domain" in
wxios_domain_param)