bug#27648: 25.2; ruby-mode doesn't see an `if` block that assigned from newline after '\'

[ojab@ojab.ru]

`ruby-mode` doesn't see an 'if' block in the following case:
```
def foo
  bar = \
    if true
      true
    else
    end
end
```
actual indentation is:
```
def foo
  bar = \
    if true
  true
else
end
end
```
and the first `end` is recognized as the end of `def` block.


In GNU Emacs 25.2.1 (x86_64-unknown-linux-gnu)
 of 2017-04-26 built on ojab.ru
System Description:	Linux From Scratch

Configured using:
 'configure --prefix=/usr --localstatedir=/var --without-all
 --enable-acl --without-x --with-zlib --with-gnutls --with-xml2
 --with-modules --with-file-notification'

Configured features:
NOTIFY ACL GNUTLS LIBXML2 ZLIB MODULES

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  value of $LC_CTYPE: en_US.UTF-8
  value of $LANG: en_RU.UTF-8
  locale-coding-system: utf-8-unix

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  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

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Memory information:
((conses 16 81921 6346)
 (symbols 48 18715 0)
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 (strings 32 13939 4754)
 (string-bytes 1 400815)
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 (heap 1024 34947 1946))