Be consistent about using 'module' for m4_module types and

Be consistent about using 'module' for m4_module types and
'handle' for lt_dlhandle types:

* m4/m4private.h (m4_symbol_value): Rename handle element to
method.  Changed all references.
(VALUE_MODULE, SYMBOL_MODULE): Renamed from VALUE_HANDLE and
SYMBOL_HANDLE respectively.  Changed all references.
* m4/m4module.h (M4INIT_HANDLER, M4FINISH_HANDLER): Ditto.
* m4/builtin.c (m4_builtin_find_by_name)
(m4_builtin_find_by_func): Use module as the parameter name for
pointers of type 'm4_module'.
* m4/module.c (module_remove, m4_get_module_name)
(install_builtin_table, install_macro_table)
(m4_module_make_resident, m4__module_next, m4_module_refcount):
Ditto.
* src/freeze.c (produce_module_dump): Ditto.
* m4/input.c (m4_input_block): Rename handle element to method.
Changed all references.
* m4/symtab.c (m4__symtab_remove_module_references): Ditto.
* modules/load.c: Use module as the variable name for pointers
of type 'm4_module'.
* modules/m4.c: Ditto.
* modules/perl.c: Ditto.
* modules/shadow.c: Ditto.