diff_match_patch: -unused import

Cherry-pick f9472d205d86c1e2c80d64b58c85e3669392d20d which reapplies svn
path=/src/trunk/; revision=16884

Conflicts:

	translate/misc/diff_match_patch.py
diff_match_patch: Postpone import

Cherry-pick ad7dd2e68b77ad45ee5c25b0388328aec02238e3 reapply svn
path=/src/trunk/; revision=16970

Conflicts:

	translate/misc/diff_match_patch.py
diff_match_patch: docstring fixes.

Cherry-pick 70e88d3b7788509c3c69404b56db4f8b17ee5c9c to reapply
docstring fixes.

Conflicts:

	translate/misc/diff_match_patch.py