Parameters read by syn_alm_cxx:

nlmax (integer):
  maximum order of l

nmmax (integer):
  maximum order of m (must not be larger than nlmax, default=nlmax)

infile (string):
  input file containing the CMB power spectrum

outfile (string):
  output file name for the calculated a_lm

rand_seed (integer):
  random-number seed

fwhm_arcmin (real):
  FWHM (in arcmin) of a Gaussian beam, which is used to smooth the
  resulting sky a_lm (default=0)

polarisation (bool):
  if false, only the intensity a_lm are generated,
  if true, T, G and C a_lm are generated

double_precision (bool, default=false):
  if false, the a_lm are created in single precision,
  otherwise in double precision.