This adds support for setting the default value used when padding image
sections. Previously 0xff was used but some targets have an erased value
of 0x00.
Change-Id: If3df6fea3abf95b09daa3ff7be362acf991070ce
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1635
Tested-by: jenkins