nvcc had some problems with gcc 12.1 stl map templates when compiling gpu.cu.
And since ldgm-session-gpu.h which contained the c++ code was only needed for
this one macro, it's probably better to move it to gpu.cuh which is
already included by all files that need it.
Doesn't differ from main.cpp much and it is in history, anyways.
This change is mostly to allow batch removal of .orig files in repo
without affecting a tracked file.
This reduces sources size by a great deal - matrices occupied some
33 MBs.
Seems useless - matrices are should be perhaps reconstructed by
matrix-gen but seem incompatible with current version (doesn't
have k/m/c header).
The scripts are not compatible with current version (and used data/
is missing).
