[kernel] Deprecates Db.Main

src/plugins/sparecode/register.ml

src/plugins/users/users_register.ml

src/plugins/variadic/tests/declared/called_in_ghost.ml

src/plugins/wp/RegionAnalysis.ml

src/plugins/wp/register.ml

src/plugins/wp/tests/wp/stmtcompiler_test.ml

src/plugins/wp/tests/wp/stmtcompiler_test_rela.ml

tests/builtins/big_local_array_script.ml

tests/callgraph/function_pointer.ml

tests/cil/Change_formals.ml

tests/cil/change_to_instr.ml

tests/cil/insert_formal.ml

tests/cil/mkBinOp.ml

tests/cil/queue_ghost_instr.ml

...constant_propagation/introduction_of_non_explicit_cast.ml

tests/crowbar/mutable_const_fail.ml

tests/crowbar/mutable_mutable_fail.ml

tests/dynamic/abstract2.ml

tests/float/fval_test.ml

tests/jcdb/jcdb.ml