bugfix for 10472

and some whitespace to follow code guidelines

unified lastIndexOf(string,dchar)

bugfix for 10472

and some whitespace to follow code guidelines

whitespace again

git is good, Im with stupid

forgot one to!dchar
Merge pull request #1374 from burner/10472

bugfix for 10472 - lastIndexOf(string, string) does not find single character string at beginning of string
[trivial] fix code style
[trivial] Use ddoc unittest
[trivial] unittest code clean up
Make std.string module CTFEable