add support for loading plugins for fixes

examples/plugins/nve2plugin.cpp

@@ -0,0 +1,30 @@
+
+#include "lammpsplugin.h"
+
+#include "version.h"
+
+#include <cstring>
+
+#include "fix_nve2.h"
+
+using namespace LAMMPS_NS;
+
+static Fix *nve2creator(LAMMPS *lmp, int argc, char **argv)
+{
+    return new FixNVE2(lmp, argc, argv);
+}
+
+extern "C" void lammpsplugin_init(void *lmp, void *handle, void *regfunc)
+{
+  lammpsplugin_t plugin;
+  lammpsplugin_regfunc register_plugin = (lammpsplugin_regfunc) regfunc;
+
+  plugin.version = LAMMPS_VERSION;
+  plugin.style   = "fix";
+  plugin.name    = "nve2";
+  plugin.info    = "NVE2 variant fix style v1.0";
+  plugin.author  = "Axel Kohlmeyer (akohlmey@gmail.com)";
+  plugin.creator2 = (lammpsplugin_factory2 *) &nve2creator;
+  plugin.handle  = handle;
+  (*register_plugin)(&plugin,lmp);
+}