this new pass, currently just a copy of pass_clang, will be for
clang_delta passes that are used in binary search mode -- just like
the line delta passes.

unfortunately there's no enough commonality with either pass_clang or
pass_line to make this just a hack to one of those, I don't think.
remove unneeded debugging code
tell build system about the new pass
partial implementation of this
one more debugging thing to remove
new pass not working quite, but mostly
move a verbose printout to a place where it makes more sense
this isn't working yet
comment out the new, not-working patch