* gc.c: fix around GC_DEBUG.
* gc.c (RVALUE::line): should be VALUE. On some environment
  (such as mswin64), `int' introduces alignment mismatch.
* gc.c (newobj_of): add an assertion to check VALUE alignment.
* gc.c (aligned_malloc): `&' is low priority than `=='.
* gc.c: define GC_DEBUG everytime and use it as value 0 or 1.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42624 b2dd03c8-39d4-4d8f-98ff-823fe69b080e