[PATCH] Fix fallout from r219557

[Anton Korobeynikov]

Ok, the reason for objc tests to fail is that we're loosing typedefs when using the type from UsualArithmeticConversions().

Consider the following code:

```
typedef long NSInteger;

int printf(const char * restrict, ...);

void foo(void) {
  NSInteger i = 0;
  printf("%s", i ? i : i);
}
```

AST before was:

```
     `-ConditionalOperator 0x7f9d1086e978 <col:16, col:24> 'NSInteger':'long'
        |-ImplicitCastExpr 0x7f9d1086e930 <col:16> 'NSInteger':'long' <LValueToRValue>
        | `-DeclRefExpr 0x7f9d1086e8b8 <col:16> 'NSInteger':'long' lvalue Var 0x7f9d1086e780 'i' 'NSInteger':'long'
        |-ImplicitCastExpr 0x7f9d1086e948 <col:20> 'NSInteger':'long' <LValueToRValue>
        | `-DeclRefExpr 0x7f9d1086e8e0 <col:20> 'NSInteger':'long' lvalue Var 0x7f9d1086e780 'i' 'NSInteger':'long'
        `-ImplicitCastExpr 0x7f9d1086e960 <col:24> 'NSInteger':'long' <LValueToRValue>
          `-DeclRefExpr 0x7f9d1086e908 <col:24> 'NSInteger':'long' lvalue Var 0x7f9d1086e780 'i' 'NSInteger':'long'
```

AST now is:

```
      `-ConditionalOperator 0x7ff93a01c178 <col:16, col:24> 'long'
        |-ImplicitCastExpr 0x7ff93a01c130 <col:16> 'NSInteger':'long' <LValueToRValue>
        | `-DeclRefExpr 0x7ff93a01c0b8 <col:16> 'NSInteger':'long' lvalue Var 0x7ff93a01bf80 'i' 'NSInteger':'long'
        |-ImplicitCastExpr 0x7ff93a01c148 <col:20> 'NSInteger':'long' <LValueToRValue>
        | `-DeclRefExpr 0x7ff93a01c0e0 <col:20> 'NSInteger':'long' lvalue Var 0x7ff93a01bf80 'i' 'NSInteger':'long'
        `-ImplicitCastExpr 0x7ff93a01c160 <col:24> 'NSInteger':'long' <LValueToRValue>
          `-DeclRefExpr 0x7ff93a01c108 <col:24> 'NSInteger':'long' lvalue Var 0x7ff93a01bf80 'i' 'NSInteger':'long'
```

Note that the type of ConditionalOperator changed. Is this expected? The special (darwin) case which looks for typedef is inside CheckPrintfHandler::checkFormatExpr()

http://reviews.llvm.org/D6217