updated BOAST sources to support version 0.9995+
Added a preprocessor directive to get_model_parameters to fail out if a CEM model is specified, but configure was run witout CEM
Merge branch 'devel' of https://github.com/geodynamics/specfem3d_globe into devel
Merge branch 'devel' of github.com:Nanosim-LIG/specfem3d_globe into devel
removed src/auxiliaries/combine_vol_data_shared.f90, which contained routines duplicated from other files of the code (that is dangerous, and very uneady to maintain the same routines twice, in two different files of the code).
Thus temporarily had to comment out xcombine_vol_data* from Makefile.in and from src/auxiliaries/rules.mk because I do not know how to fix the Makefile (probably not difficult, but I am not familiar with that).
Also removed unused variables introduced by the CEM modification a few days ago.
Added comments for ellipticity.
Removed useless white spaces using a cleaning script.