Define fmt.f_module_name

[ltaylor16]

This is used in statements as

        "f_module": {
            "{f_module_name}": [
                "{f_kind}"
            ]
        },

Change statments groups to use {f_module_name} instead of {typemap.f_module_name} to allow a default module name to be detected and avoid adding USE statement. For example, with CHARACTER arguments which do not use C_CHAR in the Fortran argument declaration.

This allows several groups to be removed: f_mixin_declare-fortran-arg-no-module, f_mixin_declare-fortran-result-no-module and f_mixin_kind-argument.