Fix an illegal memory access when creating DLLs.

	PR 29006
	* pe-dll.c (dll_name): Delete, replacing with..
	(dll_filename): ..this, moved earlier in file.
	(generate_edata): Delete parameters.  Don't set up dll_name here..
	(pe_process_import_defs): ..instead set up dll_filename and
	dll_symname here before returning.
	(dll_symname_len): Delete write-only variable.
	(pe_dll_generate_implib): Don't set up dll_symname here.