Installation issues on Ubuntu 16.04 LTS

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I get many warnings similar to this when installing with luarocks using gcc 5.4.0 on Ubuntu 16.04 LTS:

/tmp/luarocks_cephes-0-0-5487/torch-cephes/cephes/bessel/yn.c: In function ‘torch_cephes_yn’:
/tmp/luarocks_cephes-0-0-5487/torch-cephes/cephes/bessel/yn.c:85:17: warning: implicit declaration of function ‘y0’ [-Wimplicit-function-declaration]
  return( sign * y0(x) );

/tmp/luarocks_cephes-0-0-5487/torch-cephes/cephes/misc/expn.c:124:14: warning: incompatible implicit declaration of built-in function ‘log’