lib_dec.c converted to fixed point.

[x] Functions present in lib_dec.c are modified by using appropriate basops/macros/typedefs.
[x] Some buffers are present in float format still, as they were just getting passed to other modules and their processing in floating point is being done in those modules. So, these buffers are needed to be updated here as well once these dependent modules are converted.

pytest results:
pytest-mld-dec: 573 failed, 1 passed, 381 skipped
pytest-mld-dec-lev-10: 573 failed, 1 passed, 381 skipped
pytest-mld-dec-lev+10: 573 failed, 1 passed, 381 skipped.