Fixes PR 17994 - which reported that dlltool was not deleting temporary files if...

Fixes PR 17994 - which reported that dlltool was not deleting temporary files if it encounters a fatal error.

	PR binutils/17994
	* dlltool.c (temp_file_to_remove): New local array.
	(unlink_temp_files): New functions - unlinks any file in the
	temp_file_to_remove array, unless dotdeltemps is set.
	(gen_exp_file): Add temp files to array.
	(make_head): Likewise.
	(make_delay_head): Likewise.
	(make_tail): Likewise.
	(gen_lib_file): Call unlink_temp_files.