Unused parameters in encoder core-coder structure

The encoder core-coder structure st contains several unused parameters or substructures. It is proposed to remove them, namely:

• input_frame_fx
• last_element_mode
• extl_orig
• extl_brate_orig
• mem_deemph_fx
• mem_hp20_in_fx[5]
  • st_ivas->mem_hp20_in_fx should be used instead
• hPVQ
• cna_dirac_flag
• etc.

Moreover, several BWE-related parameters should be moved from st->xx under the related substructure st->hTD_BWE_TD->xx.