Merged splint subroutines.

cmake/source_list_KKRhost.txt

cmake/source_list_KKRimp.txt

cmake/source_list_voronoi.txt

source/KKRhost/generalpot.f90

source/KKRimp/interpolpot-splint.f

source/KKRscatter/csout_spline.f

source/KKRscatter/interpolspline.f

source/KKRscatter/makefile

source/KKRscatter/splint.f

source/KKRscatter/splint_complex.f

source/KKRscatter/splint_real.f

source/common/interpolspline.f90

source/common/splint.f90

source/voronoi/genpotstart12.f

source/voronoi/jellstart12.f

source/voronoi/splint.f