[libclang] Make sure that when we have multiple @class references in the same line,

[libclang] Make sure that when we have multiple @class references in the same line,
that later ones do not override the previous ones.

If we have:
   @class Foo, Bar;
source ranges for both start at '@', so 'Bar' will end up overriding
'Foo' even though the cursor location was at 'Foo'.

rdar://11257578

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154873 91177308-0d34-0410-b5e6-96231b3b80d8