[libclang] Fix getting a cursor that points inside tag definition that is part

of a type specifier.

e.g. for:

typedef struct _MyS {
  int foo;
} MyS;

pointing at field 'foo' would give a cursor for the typedef declaration 'MyS'
instead of the field.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@138593 91177308-0d34-0410-b5e6-96231b3b80d8