Fix compile time warning messages about variables being used before they are initialised.

Fix compile time warning messages about variables being used before they are initialised.

	PR 18313
bin	* ieee.c (ieee_read_cxx_class): Initialise the varargs variable.
	* readelf.c (uncompress_section_contents): Zero initialise the
	zstream structure.

bfd	* compress.c (decompress_contents): Zero initialse the z_stream
	structure.