std.string doc issue11895

std.algorithm style doc header

https://issues.dlang.org/show_bug.cgi?id=11895

preview:
http://burner.github.io/phobos/phobos-prerelease/std_string.html
Why are `startsWith` and `endsWith` repeated here? They have already been mentioned in the previous category. (Plus, they are broken links 'cos there are no such functions in this module.)