Remove `Vcomp_sym_subr_c_name_h'

Remove `Vcomp_sym_subr_c_name_h'

Given there's no more unique relation symbol-name -> c-name remove
`Vcomp_sym_subr_c_name_h' and store the c_name directly in struct
Lisp_Subr.  The old approach would have failed dumping two functions
with the same symbol-name.

	* src/lisp.h (struct Lisp_Subr): Add 'native_c_name' field.

	* src/pdumper.c (dump_subr): Update hash + dump 'native_c_name'.
	(dump_cold_native_subr): dump 'native_c_name'.
	(dump_do_dump_relocation): Update logic for reviving using
	'native_c_name'.

	* src/comp.c (make_subr): Update for 'native_c_name' field.
	(Fcomp__register_lambda, Fcomp__register_subr): Clean-up code for
	'Vcomp_sym_subr_c_name_h' removal.
	(syms_of_comp): Remove 'Vcomp_sym_subr_c_name_h'.