Summary:
The string class contains methods which support receiving either a string literal or a string object.
For example, calls to append can receive either a char* or a string.
```
string& append (const string& str);
string& append (const char* s);
```
Which make these cases equivalent, and the .c_str() useless:
```
std::string s = "123";
str.append(s);
str.append(s.c_str());
```
In these cases, removing .c_str() doesn't provide any size or speed improvement.
It's only a readability issue.
If the string contains embedded NUL characters, the string literal and the string
object won't produce the same semantic.
Reviewers: alexfh, sbenza
Subscribers: LegalizeAdulthood, aaron.ballman, chapuni, Eugene.Zelenko, cfe-commits
Differential Revision: http://reviews.llvm.org/D18475
llvm-svn: 266463
9cfd8cea6b