gc.c: RB_GC_GUARD should be robust enough for any compiler

* include/ruby/ruby.h (RB_GC_GUARD):
  use rb_gc_guarded_ptr_val on non-GCC/MSC
* gc.c (rb_gc_guarded_ptr_val): rename and adjust argument.
  RB_GC_GUARD should be robust enough for any compiler.
  [ruby-core:60816] [Bug #7805]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45064 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-02-21

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45065 b2dd03c8-39d4-4d8f-98ff-823fe69b080e