add message about -DLAMMPS_BIGBIG incompatibility of scatter/gather functions

doc/src/Howto_library.txt

@@ -166,9 +166,6 @@ void lammps_gather_atoms_subset(void *, char *, int, int, int, int *, void *)
 void lammps_scatter_atoms(void *, char *, int, int, void *)
 void lammps_scatter_atoms_subset(void *, char *, int, int, int, int *, void *) :pre
 
-void lammps_create_atoms(void *, int, tagint *, int *, double *, double *,
-                         imageint *, int) :pre
-
 The gather functions collect peratom info of the requested type (atom
 coords, atom types, forces, etc) from all processors, and returns the
 same vector of values to each calling processor.  The scatter
@@ -176,6 +173,11 @@ functions do the inverse.  They distribute a vector of peratom values,
 passed by all calling processors, to individual atoms, which may be
 owned by different processors.
 
+IMPORTANT NOTE: These functions are not compatible with the
+-DLAMMPS_BIGBIG setting when compiling LAMMPS.  Dummy functions
+that result in an error message and abort will be subsituted
+instead of resulting in random crashes and memory corruption.
+
 The lammps_gather_atoms() function does this for all N atoms in the
 system, ordered by atom ID, from 1 to N.  The
 lammps_gather_atoms_concat() function does it for all N atoms, but
@@ -196,6 +198,9 @@ those values to each atom in the system.  The
 lammps_scatter_atoms_subset() function takes a subset of IDs as an
 argument and only scatters those values to the owning atoms.
 
+void lammps_create_atoms(void *, int, tagint *, int *, double *, double *,
+                         imageint *, int) :pre
+
 The lammps_create_atoms() function takes a list of N atoms as input
 with atom types and coords (required), an optionally atom IDs and
 velocities and image flags.  It uses the coords of each atom to assign