Xcode 4.4 compile error in DiffMatchPatchTest.m (trivial fix)

```
What steps will reproduce the problem?
1. Attempt to compile in Xcode 4.4
2. See errors in line 841 of DiffMathPatchTest.m

Please provide any additional information below.

Fix is simple:

--- a/Tests/DiffMatchPatchTest.m
+++ b/Tests/DiffMatchPatchTest.m
@@ -838,8 +838,8 @@
diffs = [NSMutableArray arrayWithObjects:[Diff diffWithOperation:DIFF_DELETE andText:@"Apple"], [
STAssertEqualObjects(diffs, [dmp diff_mainOfOldString:@"Apples are a fruit." andNewString:@"Banan

- diffs = [NSMutableArray arrayWithObjects:[Diff diffWithOperation:DIFF_DELETE
andText:@"a"], [Diff
- NSString *aString = [NSString stringWithFormat:@"\U00000680x%C", 0];
+ diffs = [NSMutableArray arrayWithObjects:[Diff diffWithOperation:DIFF_DELETE
andText:@"a"], [Diff
+ NSString *aString = [NSString stringWithFormat:@"\U00000680x%C", (unichar)
0];
STAssertEqualObjects(diffs, [dmp diff_mainOfOldString:@"ax\t" andNewString:aString checkLines:NO]

diffs = [NSMutableArray arrayWithObjects:[Diff diffWithOperation:DIFF_DELETE andText:@"1"], [Diff

```

Original issue reported on code.google.com by `alans...@gmail.com` on 3 Aug 2012 at 12:08