Hardening silk/fixed

silk/fixed/apply_sine_window_FIX.c

silk/fixed/burg_modified_FIX.c

silk/fixed/encode_frame_FIX.c

silk/fixed/find_LPC_FIX.c

silk/fixed/find_pitch_lags_FIX.c

silk/fixed/find_pred_coefs_FIX.c

silk/fixed/pitch_analysis_core_FIX.c

silk/fixed/residual_energy16_FIX.c

silk/fixed/residual_energy_FIX.c

silk/fixed/schur64_FIX.c

silk/fixed/schur_FIX.c

silk/fixed/warped_autocorrelation_FIX.c