Add asserts to Log2_norm_lc() and log10_fx()

Basic info

• Fixed point:
  • Encoder (fixed): 24e8bdab
  • Decoder (fixed): 24e8bdab

Bug description

The functions Log2_norm_lc() and log10_fx() both use table-lookup. Given that the address sanitizer doesn't reliably work if the OOB-access is too far off the original table, I would like to add some asserts to these functions to catch OOB early, at least while NDBUG isn't set.