Summary:
This makes the formatter of raw string literals use NestedBlockIndent for
determining the 0 column of the content inside. This makes the formatting use
less horizonal space and fixes a case where two newlines before and after the
raw string prefix were selected instead of a single newline after it:
Before:
```
aaaa = ffff(
R"pb(
key: value)pb");
```
After:
```
aaaa = ffff(R"pb(
key: value)pb");
```
Reviewers: djasper, sammccall
Reviewed By: sammccall
Subscribers: klimek, cfe-commits
Differential Revision: https://reviews.llvm.org/D44141
llvm-svn: 326996
a71f626eac