The `__future__` we relied on is now, where the 3 specific things are
all included [since Python 3.0](https://docs.python.org/3/library/__future__.html):
* absolute_import
* print_function
* unicode_literals
* division
These import statements are no-ops and are no longer necessary.
* E101: indentation contains mixed spaces and tabs
* E111: indentation is not a multiple of four
* E128: continuation line under-indented for visual indent
* E302: expected 2 blank lines, found 1
* W191: indentation contains tabs
Compute the hash of all interface tokens when parsing; write the
interface hash to the swiftdeps file, or if the -dump-interface-hash
option is passed to the frontend. This hash will be used in incremental
mode to determine whether a file's interface has changed, and therefore
whether dependent files need to be rebuilt in response to the change.
Committed on ChrisW's behalf while he gets his setup unborked.
rdar://problem/15352929
Swift SVN r30477
