Replace C++ style line comments with C style line comments.

Replace C++ style line comments with C style line comments.
(symbian_add_attribute): Do not use a ? operator on the LHS of an assignment.
(sh_symbian_handle_dll_attribute): Change the type of the method vector to
  "VEC(tree,gc)*" and use vector accessor macros to walk over the elements.
(symbian_export_vtable_and_rtti_p): Likewise.
(symbian_class_needs_attribute_p): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@102228 138bc75d-0d04-0410-961f-82ee72b054a4