Summary:
This patch adds the support for detecting suspicious string
literals and their //incorrect// usage.
The following example shows a incorrect character escaping leading
to an embedded NUL character.
```
std::string str = "\0x42"; // Should be "\x42".
```
The patch also add detection of truncated literal when a literal
is passed to a string constructor.
Reviewers: hokein, alexfh
Subscribers: LegalizeAdulthood, bcraig, Eugene.Zelenko, bkramer, cfe-commits
Differential Revision: http://reviews.llvm.org/D18783
llvm-svn: 265691
Etienne Bergeron