move SWIG support to tools/swig folder

cmake/CMakeLists.txt

@@ -382,7 +382,7 @@ endforeach()
 # optionally enable building script wrappers using swig
 option(WITH_SWIG "Build scripting language wrappers with SWIG" OFF)
 if(WITH_SWIG)
-  get_filename_component(LAMMPS_SWIG_DIR ${LAMMPS_SOURCE_DIR}/../swig ABSOLUTE)
+  get_filename_component(LAMMPS_SWIG_DIR ${LAMMPS_SOURCE_DIR}/../tools/swig ABSOLUTE)
   get_filename_component(LAMMPS_SWIG_BIN ${CMAKE_BINARY_DIR}/swig ABSOLUTE)
   add_subdirectory(${LAMMPS_SWIG_DIR} ${LAMMPS_SWIG_BIN})
 endif()

tools/README

@@ -46,6 +46,7 @@ replica                tool to reorder LAMMPS replica trajectories according to
 singularity            Singularity container descriptions suitable for LAMMPS development
 smd                    convert Smooth Mach Dynamics triangles to VTK
 spin                   perform a cubic polynomial interpolation of a GNEB MEP
+swig                   SWIG generated script language wrappers for the LAMMPS C library interface
 valgrind               suppression files for use with valgrind's memcheck tool
 vim                    add-ons to VIM editor for editing LAMMPS input scripts
 xmgrace                a collection of scripts to generate xmgrace plots