Fix layouting of tokens with a leading escaped newline.

If a token follows directly on an escaped newline, the escaped newline
is stored with the token. Since we re-layout escaped newlines, we need
to treat them just like normal whitespace - thus, we need to increase
the whitespace-length of the token, while decreasing the token length
(otherwise the token length contains the length of the escaped newline
and we double-count it while indenting).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171706 91177308-0d34-0410-b5e6-96231b3b80d8