util: Improved qemu_hexmap() to include an ascii dump of the buffer

util: Improved qemu_hexmap() to include an ascii dump of the buffer

qemu_hexdump() in util/hexdump.c has been changed to give also include a
ascii dump of the buffer. Also, calls to hex_dump() in net/net.c have
been replaced with calls to qemu_hexdump(). This takes care of two misc
BiteSized Tasks.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Isaac Lozano <109lozanoi@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>