Clean-up or document remaining debug-switches in code

There are still a number of debugging-switches in the code which aren't documented in options.h. I'm wondering, whether these could be removed or whether they should at least be documented in options.h.

What I've found:

• ./lib_dec/ivas_spar_md_dec.c:#ifdef DEBUG_SPAR_DIRAC_WRITE_OUT_PRED_PARS @millsa
• ./lib_dec/ivas_stereo_dft_dec.c:#ifdef DBG_TD_STEFI @fotopoulou
• ./lib_dec/ivas_stereo_ica_dec.c:#ifdef QC_DBG_DFT_NO_SHIFT_DEC @malenovsky
• ./lib_dec/ivas_stereo_icbwe_dec.c:#ifdef QC_DBG_ICBWE @malenovsky
• ./lib_enc/ivas_mcmasa_enc.c:#ifdef DISABLE_DIRAC_DELAY_COMP @malenovsky
• ./lib_enc/ivas_spar_encoder.c:#ifdef DEBUG_SPAR_DIRAC_WRITE_OUT_PRED_PARS @millsa
• ./lib_enc/ivas_spar_encoder.c:#if 0 /* SBA_TD_RESIDUAL */ @millsa
• ./lib_enc/ivas_stereo_dft_enc.c:#ifdef DEBUG_MODE_DFT_BITS @fotopoulou
• ./lib_enc/ivas_stereo_dft_enc_itd.c:#ifdef DEBUG_STEREO_CLF @malenovsky
• ./lib_enc/ivas_stereo_td_analysis.c:#ifdef FORCE_RATIO_L_0 @malenovsky
• ./lib_enc/lib_enc.c:#if 0 // IVAS_fmToDo: temporary disabled to keep EVS bit-exactness -> to be verified @multrus -> moved to #714 (closed)
• ./lib_enc/ivas_stereo_icbwe_enc.c:#ifdef QC_DBG_ICBWE @malenovsky
• ./lib_enc/ivas_decision_matrix_enc.c:#ifdef DBG_STEREO_ICBWE2_TBE2K8 @malenovsky