fix Issue 10078 - std.string.indexOf fails at compile time
Merge pull request #1417 from dawgfoto/fix10078

fix Issue 10078 - std.string.indexOf fails at compile time
[trivial] fix code style
[trivial] Use ddoc unittest
[trivial] unittest code clean up
Make std.string module CTFEable
Merge pull request #1415 from 9rnsr/CTFEablePhobos

Make std.string module CTFEable