Programs that want to background themselves now need to define threadmaybackground returning 1. This avoids a confusing (to people and debuggers) extra parent process for all the threaded programs that will never want to background themselves.

Remote whitespace at the ends of lines. Remove blank lines from the ends of files. Change modes on source files so that they are not executable. Signed-off-by: Dan Cross <cross@gajendra.net>

R=rsc http://codereview.appspot.com/6744054