Efficiency:
- from Andreas Enge 16 September 2008:
  Once mpc_sin_cos exists, improve mpc_tan to use it

New functions to implement:
- from Philippe Théveny 25 September 2008:
  mpc_get_real/mpc_get_imag for copying the real and
  imaginary part, and mpc_realref/mpc_imagref for returning
  pointers to them (MPC_RE and MPC_IM already do the job)
- from Andreas Enge 16 September 2008:
  mpc_sin_cos; needs mpfr_sinh_cosh
- from Mickael Gastineau <gastineau@imcce.fr> 14 Apr 2008:
  mpc_fma: d=a*b+c
- from Andreas Enge 9 April 2008:
  mpc_pow_ui
- from Andreas Enge 9 April 2008:
  depending on a preprocessor variable (DEBUG or MPC_LOG), add
  logging: For each function call, output arguments and precision, and
  the successive precisions in the main loop; allows to test with
  real world data whether we hit corner cases
  possibly: mpc_write and mpc_read that serialises mpc objects (output in
  base 16 together with the precision of the variable)
- from Andreas Enge and Philippe Théveny 9 April 2008
  work plan for completing functionality
  1) inverse trigonometric functions
  2) cproj at any moment (relatively easy)
- from Andreas Enge and Philippe Théveny 17 July 2008
  agm (and complex logarithm with agm ?)

New tests to add:
- from Andreas Enge and Philippe Théveny 9 April 2008
  correct handling of Nan and infinities in the case of
  intermediate overflows while the result may fit (we need special code)