[kernel] Extract from Cil the visitor for const globals substitution into a new file.

Makefile

headers/header_spec.txt

src/kernel_internals/typing/substitute_const_globals.ml

src/kernel_internals/typing/substitute_const_globals.mli

src/kernel_services/ast_queries/cil.ml

src/kernel_services/ast_queries/cil.mli

src/kernel_services/ast_queries/file.ml