merge revision(s) 7ff1bf31,e89d8070: [Backport #18516]

    An alias can suppress method redefinition warning

    ---
     test/ruby/test_alias.rb | 11 +++++++++++
     1 file changed, 11 insertions(+)

    Fix memory leak at the same named alias [Bug #18516]

    When aliasing a method to the same name method, set a separate bit
    flag on that method definition, instead of the reference count
    increment.  Although this kind of alias has no actual effect at
    runtime, is used as the hack to suppress the method re-definition
    warning.
    ---
     method.h                |  1 +
     test/ruby/test_alias.rb | 18 ++++++++++++++++++
     vm_method.c             |  9 ++++++++-
     3 files changed, 27 insertions(+), 1 deletion(-)