* gc.c (is_incremental_marking): use #if/#else because
  rb_objspace_t::flags::during_incremental_marking is not defined
  when GC_ENABLE_INCREMENTAL_MARK is 0.
* gc.c (will_be_incremental_marking, is_full_marking): similar fix.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48335 b2dd03c8-39d4-4d8f-98ff-823fe69b080e