ivas_td_low_rate_dec converted to fixed point.

[x]Implemented td_low_rate_dec_fx and re-implemented some EVS functions with IVAS specific processing (disabled under ADD_LRTD macro).

[x]Examples:

• bands_and_bit_alloc_ivas_fx required conversion of additional bit allocation processing.\
• GSC_gain_adj_ivas_fx required an additional gain factor from IVAS code.\
• highband_exc_dct_in_ivas_fx required addition of scaling code.\
• gsc_dec_ivas_fx required change in one of the if conditions which was causing bit reading issues and also required addition of scaling code.

MLD:
Original: 7 cases > 5
8.596422 9.193538 10.831529 10.852825 12.477127 22.267653 22.510826

+10dB: 24 cases > 5
5.383359 5.663041 5.663041 6.327166 6.613963 6.970016 7.061517 7.339634 7.782482 7.857953 8.255404 10.755767 10.755767 11.33441 14.461291 15.203072 16.607782 16.9758 17.577797 19.374035 19.76078 23.787466 27.369797 39.378357

-10dB: 5 cases > 5
5.964953 6.009441 9.042313 14.816738 15.979668