Summary: This patch implements 4.3 of http://open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4220.pdf. If a raw string contains a newline character, replace each newline character with the \n escape code. Without this patch, included test case (macro_raw_string.cpp) results compilation failure.

Reviewers: rsmith, doug.gregor, jkorous-apple

Reviewed By: jkorous-apple

Subscribers: jkorous-apple, vsapsai, cfe-commits

Differential Revision: https://reviews.llvm.org/D39279

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@319904 91177308-0d34-0410-b5e6-96231b3b80d8