Moved define_bc files into subdirectory and modified Makefile accordinly

src/Makefile

@@ -23,20 +23,22 @@ compute_positive_volume.o \
 compute_normals.o \
 create_surfaces.o \
 define_bc.o \
-define_bc_2Dpunch.o \
-define_bc_2Dpunch_vert.o \
-define_bc_3Dpunch.o \
-define_bc_folding.o \
-define_bc_jgr.o \
-define_bc_model1.o \
-define_bc_nest.o \
-define_bc_parallipipede.o \
-define_bc_pipo.o \
-define_bc_riedel.o \
-define_bc_ritske.o \
-define_bc_ritske_isurf.o \
-define_bc_sphere.o \
-define_bc_subduction.o \
+define_bcs/define_bc_2Dpunch.o \
+define_bcs/define_bc_2Dpunch_vert.o \
+define_bcs/define_bc_3Dpunch.o \
+define_bcs/define_bc_folding.o \
+define_bcs/define_bc_jgr.o \
+define_bcs/define_bc_model1.o \
+define_bcs/define_bc_nest.o \
+define_bcs/define_bc_parallipipede.o \
+define_bcs/define_bc_pipo.o \
+define_bcs/define_bc_riedel.o \
+define_bcs/define_bc_ritske.o \
+define_bcs/define_bc_ritske_isurf.o \
+define_bcs/define_bc_segmented_s-line.o \
+define_bcs/define_bc.sphere.o \
+define_bcs/define_bc_sphere.o \
+define_bcs/define_bc_subduction.o \
 define_isostasy_bc.o \
 define_surface.o \
 define_cloud.o \