text: Title: Load full native fastText Facebook model is partial
  Body: #### Problem description
  
  Hidden vectors are bad. I'm using the gensim.models.fasttext.load_facebook_model function to load the .bin file, but the syn1 fails loading. Also trainables.syn1neg is full of zeros.
  
  'FastTextTrainables' object has no attribute 'syn1'
  
  #### Steps/code/corpus to reproduce
  
  Simply using `ft = gensim.models.fasttext.load_facebook_model(fname)`  on Facebook's model.
  Then `ft.syn1` or `ft.trainables.syn1neg` which returns the zero array.
  
  #### Versions
  
  Please provide the output of:
  Windows-2012ServerR2-6.3.9600-SP0
  Python 3.7.1 (default, Dec 10 2018, 22:54:23) [MSC v.1915 64 bit (AMD64)]
  Bits 64
  NumPy 1.18.3
  SciPy 1.4.1
  gensim 3.8.3
  FAST_VERSION 0
  
  